[General Questions and Answers] kossieh:
Ok, just a major update:

I have downloaded some files from this website and it seems that this file has some kind of script, that could be used to make bootable ROM.

Actually, it is a updater-script, which (AFAIK) is also used anywhere else. According to my cat /proc/cpuinfo, the only thing that needs to be done is to compile "su" binary for the platform and then it could be used to flash the SU (understand it as create a ROOT and UNROOT zips to do the job). Then install some kind of root app (SuperSU or Superuser, depends - probably) and then it could be done.

Question is about CWM, if the bootloader permits to load a tempovary CWM (as I did on my S5830i - just a note) and then install any, now modded, ROM into device.

I presume that managing partitions and filesystems would be tricky, so I WOULD LIKE to ask anyone, who is interested in futher developing. I would like to also contribute, because it makes sense. Maybe we'll be good enough to create CyanogenMod 12 (or 13?) - just to match Marshallow. Or, we can stick to 5.1 (which is good anyway) and make a clean Android ROM (personally I would appreciate that).

As promised, here is updater-script for information:

getprop("ro.product.device") == "A2010-a" || abort("This package is for \"A2010-a\" devices; this is a \"" + getprop("ro.product.device") + "\".");
show_progress(0.750000, 0);
ui_print("Patching system image unconditionally...");
block_image_update("system", package_extract_file("system.transfer.list"), "system.new.dat", "system.patch.dat");
show_progress(0.050000, 5);
assert(package_extract_file("boot.img", "/tmp/boot.img"),
write_raw_image("/tmp/boot.img", "bootimg"),
delete("/tmp/boot.img"));
assert(package_extract_file("mobicore.bin", "/tmp/tee1.img"),
write_raw_image("/tmp/tee1.img", "tee1"),
delete("/tmp/tee1.img"));
show_progress(0.200000, 10);
apply_sig(package_extract_file("sig/boot.sig"), "bootimg");

I was also surprised that this is for Lenovo A2010-a. Maybe there is only device, just A2010-a.

Also, I'm posting a "scatter.txt", I don't understand clearly, what it is, probably a flashing tool specific config? Or is it a map for the device storage?

My opinion is, that it could be a map of the device storage system, including intervals, where the storage ends and partitioning.

preloader 0x0
pgpt 0x0
proinfo 0x80000
nvram 0x380000
protect1 0x880000
protect2 0x1280000
lk 0x1c80000
para 0x1d00000
boot 0x1d80000
recovery 0x2d80000
logo 0x3d80000
expdb 0x4580000
seccfg 0x4f80000
oemkeystore 0x5000000
secro 0x5200000
keystore 0x5800000
tee1 0x6000000
tee2 0x6500000
frp 0x6a00000
nvdata 0x6b00000
metadata 0x8b00000
system 0xb000000
cache 0xab000000
userdata 0xc4000000
flashinfo 0xFFFF0084
sgpt 0xFFFF0004

The last is "type.txt", which has just one thing inside, and that is just "1". To be correct regarding to xda dev forums, also in code:

1

The package itself also contains 2 extra files (i digged directly from update.zip!) and they're:

Credits.txt

How to flash OTA file.txt

...where "How to flash OTA file.txt" contains just a description:

Copy the update.zip file to the phone SD and flash it through the stock recovery mode.

Or

Copy the update.zip file to the phone SD and flash it through the Settings > About > Check Update (only if your device support this method).

Instruction by androidxda.com.

I also downloaded all files (3 gigs in total) and I will investigate when I will have time. My wish is to call for someone who would help us with development. As stated before, I am ready to help, as well as I am sure that original author of this thread (andoruB) probably wants too...