[Android Software/Hacking General [Developers Only]] munjeni:
It can be modified to work on blockdevice too if I in next month when I get some more free time for it implement things into superunpack to modify super image on the fly, its very possible I'm believing! This confirms that all images is extracted as a RW as a start point right now to skip tune2fs and e2fsck:

root@dm920 /media/hdd/sony/rom # ../superunpack super_X-FLASH-ALL-2389.bin

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Super image dumper v_11 (by expert :) munjeni @ xda 2020)

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LpMetadataGeometry magic = 0x616c4467

LpMetadataGeometry struct size = 0x34

LpMetadataGeometry sha256 = 12FF55F0ABA7B506F25CB5DA5DCA09344234E8DF1D9C93AE82A499D98019467E

LpMetadataGeometry metadata_max_size = 0x10000

LpMetadataGeometry metadata_slot_count = 0x3

LpMetadataGeometry logical_block_size = 0x1000

LpMetadataHeader magic = 0x414c5030

LpMetadataHeader major_version = 10

LpMetadataHeader minor_version = 0

LpMetadataHeader header_size = 0x80

LpMetadataHeader header sha256 = 0719CA357247D01FF19B72E26FB357DFAB989336C7A20672AC92FFF4BA1392DE

LpMetadataHeader tables_size = 0x2e8

LpMetadataHeader tables sha256 = 51E4018E53FB27D54759546AE39118ACDD63493C0A2DE2CEC24E47D50122B912

LpMetadataHeader partitions offset = 0x0

LpMetadataHeader partitions num_entries = 0x8

LpMetadataHeader partitions entry_size = 0x34

LpMetadataHeader extents offset = 0x1a0

LpMetadataHeader extents num_entries = 0x5

LpMetadataHeader extents entry_size = 0x18

LpMetadataHeader groups offset = 0x218

LpMetadataHeader groups num_entries = 0x3

LpMetadataHeader groups entry_size = 0x30

LpMetadataHeader block_devices offset = 0x2a8

LpMetadataHeader block_devices num_entries = 0x1

LpMetadataHeader block_devices entry_size = 0x40

Partitions = 5 used, 3 not used, total 8

partition_1_name = system_a

attributes = 0x1

first_extent_index = 0x0

num_extents = 0x1

group_index = 0x1

partition_group = somc_dynamic_partitions_a

extent num_sectors = 0x3c62b8 (0x78c57000 bytes total)

extent target_type = 0x0

extent target_data = 0x800 (dumping offset = 0x100000)

extent target_source = 0x0

Filetype EXT4. EXT4 size = 0x76dc4000

Dumping system_a.ext4 ...

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Do you want system_a.ext4 RW? Typa 'y' for confirm, type 'n' to skip, and press ENTER.

y

partition_2_name = system_b

attributes = 0x1

first_extent_index = 0x1

num_extents = 0x1

group_index = 0x2

partition_group = somc_dynamic_partitions_b

extent num_sectors = 0xadbe8 (0x15b7d000 bytes total)

extent target_type = 0x0

extent target_data = 0x3c7000 (dumping offset = 0x78e00000)

extent target_source = 0x0

Filetype EXT4. EXT4 size = 0x155ed000

Dumping system_b.ext4 ...

..........................................

Do you want system_b.ext4 RW? Typa 'y' for confirm, type 'n' to skip, and press ENTER.

y

partition_3_name = product_a

attributes = 0x1

first_extent_index = 0x2

num_extents = 0x1

group_index = 0x1

partition_group = somc_dynamic_partitions_a

extent num_sectors = 0x2e77a0 (0x5cef4000 bytes total)

extent target_type = 0x0

extent target_data = 0x475000 (dumping offset = 0x8ea00000)

extent target_source = 0x0

Filetype EXT4. EXT4 size = 0x5b769000

Dumping product_a.ext4 ...

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Do you want product_a.ext4 RW? Typa 'y' for confirm, type 'n' to skip, and press ENTER.

y

partition_4_name = product_b (unused)

attributes = 0x1

first_extent_index = 0x3

num_extents = 0x0

group_index = 0x2

partition_group = somc_dynamic_partitions_b

extent num_sectors = NULL

extent target_type = NULL

extent target_data = NULL

extent target_source = NULL

Skipping dump.

partition_5_name = vendor_a

attributes = 0x1

first_extent_index = 0x3

num_extents = 0x1

group_index = 0x1

partition_group = somc_dynamic_partitions_a

extent num_sectors = 0x18b6b8 (0x316d7000 bytes total)

extent target_type = 0x0

extent target_data = 0x75c800 (dumping offset = 0xeb900000)

extent target_source = 0x0

Filetype EXT4. EXT4 size = 0x30a47000

Dumping vendor_a.ext4 ...

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Do you want vendor_a.ext4 RW? Typa 'y' for confirm, type 'n' to skip, and press ENTER.

y

partition_6_name = vendor_b (unused)

attributes = 0x1

first_extent_index = 0x4

num_extents = 0x0

group_index = 0x2

partition_group = somc_dynamic_partitions_b

extent num_sectors = NULL

extent target_type = NULL

extent target_data = NULL

extent target_source = NULL

Skipping dump.

partition_7_name = odm_a

attributes = 0x1

first_extent_index = 0x4

num_extents = 0x1

group_index = 0x1

partition_group = somc_dynamic_partitions_a

extent num_sectors = 0xb70 (0x16e000 bytes total)

extent target_type = 0x0

extent target_data = 0x8e8000 (dumping offset = 0x11d000000)

extent target_source = 0x0

Filetype EXT4. EXT4 size = 0x154000

Dumping odm_a.ext4 ...

Do you want odm_a.ext4 RW? Typa 'y' for confirm, type 'n' to skip, and press ENTER.

y

partition_8_name = odm_b (unused)

attributes = 0x1

first_extent_index = 0x5

num_extents = 0x0

group_index = 0x2

partition_group = somc_dynamic_partitions_b

extent num_sectors = NULL

extent target_type = NULL

extent target_data = NULL

extent target_source = NULL

Skipping dump.

root@dm920 /media/hdd/sony/rom # ls

odm_a.ext4 product_a.ext4 rr super_X-FLASH-ALL-2389.bin system_a.ext4 system_b.ext4 v v.c vendor_a.ext4

root@dm920 /media/hdd/sony/rom # mount system_b.ext4 rr

root@dm920 /media/hdd/sony/rom # mount

/dev/mmcblk0p2 on / type ext4 (rw,relatime,data=ordered)

devtmpfs on /dev type devtmpfs (rw,relatime,size=503448k,nr_inodes=55117,mode=755)

sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)

proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)

tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev,relatime)

devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620)

tmpfs on /run type tmpfs (rw,nosuid,nodev,relatime,mode=755)

tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)

cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd)

cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)

cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)

cgroup on /sys/fs/cgroup/net_cls type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls)

cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)

cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)

systemd-1 on /data type autofs (rw,relatime,fd=24,pgrp=1,timeout=0,minproto=5,maxproto=5,direct)

mqueue on /dev/mqueue type mqueue (rw,relatime)

tmpfs on /var/volatile type tmpfs (rw,relatime,mode=755)

tmpfs on /tmp type tmpfs (rw,relatime)

/dev/sda1 on /media/hdd type ext4 (rw,relatime,data=ordered)

fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)

/dev/mmcblk0p3 on /data type ext4 (rw,relatime,data=ordered)

/etc/auto.misc on /misc type autofs (rw,relatime,fd=6,pgrp=347,timeout=300,minproto=5,maxproto=5,indirect)

-hosts on /net type autofs (rw,relatime,fd=12,pgrp=347,timeout=300,minproto=5,maxproto=5,indirect)

/etc/auto.hotplug on /autofs type autofs (rw,relatime,fd=18,pgrp=347,timeout=300,minproto=5,maxproto=5,indirect)

/media/hdd/sony/rom/system_b.ext4 on /media/hdd/sony/rom/rr type ext4 (rw,relatime)

root@dm920 /media/hdd/sony/rom #

as you see at the end of log sucesfully mount system_b.ext4 as RW