[Acer Iconia A500] mybva:
Yes I did that before, now I found the log file saying not enough space in /system

# Begin Open GApps Install Log
------------------------------------------------------------------
ROM Android version | 5.1.1
ROM Build ID | picasso-userdebug 5.1.1 LMY49M eng.thor2002ro.20170120.114336 test-keys
ROM Version increment | eng.thor2002ro.20170120.114336
ROM SDK version | 22
ROM/Recovery modversion | OmniROM-5.1.1-20170120 Tegraowners ROM v13 (thor & digetx)
Device Recovery |
Device Name | a501
Device Model | A501
Device Type | tablet
Device CPU | armeabi-v7a,armeabi
Device A/B-partitions | false
Installer Platform | arm
ROM Platform | arm
Display Density Used | 160
Install Type | Dirty[Data NOT Wiped]
Smart ART Pre-ODEX | false [Only 6.0+]
Google Camera already installed | false
FaceUnlock Compatible | true
VRMode Compatible | false
Google Camera Compatible | true
New Camera API Compatible | false[force_api]
Google Pixel Features | false
Current GApps Version | No GApps Installed
Installing GApps Zipfile | /external_sd/open_gapps-arm-5.1-nano-20180927.zip
Installing GApps Version | 20180927
Installing GApps Type | nano
Config Type |
Using gapps-config | Not Used
Remove Stock/AOSP Browser | false[NO_Chrome]
Remove Stock/AOSP Camera | false[NO_CameraGoogle]
Remove Stock/AOSP Dialer | false[NO_DialerGoogle]
Remove Stock/AOSP Email | false[NO_Gmail]
Remove Stock/AOSP Gallery | false[NO_Photos]
Remove Stock/AOSP Launcher | false[NO_GoogleNow/PixelLauncher]
Remove Stock/AOSP MMS App | false[NO_Messenger]
Remove Stock/AOSP Pico TTS | false[NO_GoogleTTS]
Ignore Google Contacts | false
Ignore Google Dialer | false
Ignore Google Keyboard | false
Ignore Google Package Installer | false
Ignore Google NFC Tag | true[NoRemove]
Ignore Google WebView | false
Total System Size (KB) | 595136
Used System Space (KB) | 387672
Current Free Space (KB) | 207464
Additional Space Required (KB) | 33896 << See Calculations Below
------------------------------------------------------------------
# End Open GApps Install Log

INSTALLATION FAILURE: Your device does not have sufficient space available in
the system partition to install this GApps package as currently configured.
You will need to switch to a smaller GApps package or use gapps-config to
reduce the installed size.

!!! WARNING !!! - Duplicate files were found between your ROM and this GApps
package. This is likely due to your ROM's dev including Google proprietary
files in the ROM. The duplicate files are shown in the log portion below.

# Begin GApps <> ROM Duplicate File List
/system/etc/permissions/com.google.widevine.software.drm.xml
# End GApps <> ROM Duplicate File List

# Begin GApps Size Calculations
------------------------------------------------------------------
TYPE | DESCRIPTION | SIZE | TOTAL
| Current Free Space | 207464 | 207464
Remove | Existing GApps | + 4 | 207468
Remove | Obsolete Files | + 0 | 207468
Remove | extservicesstock | + 0 | 207468
Remove | extsharedstock | + 0 | 207468
Remove | provision | + 8 | 207476
Install | Core | - 99536 | 107940
Install | calsync | - 1796 | 106144
Install | facedetect | - 536 | 105608
Install | faceunlock | - 14512 | 91096
Install | search | - 76648 | 14448
Install | speech | - 39128 | -24680
| Buffer Space | - 9216 | -33896
------------------------------------------------------------------
Additional Space Required | 33896
------------------------------------------------------------------

# End GApps Size Calculations

# Begin User's gapps-config

# End User's gapps-config

So I selected the Pico version of GApps which then seemed to work :) , first I started with STOCK then NANO.

Now I need to see if Pico is enough and works with my apps I need.

Is there a way to extend system partition?

Thanks for your help!