Epic is first about upgradability [DX] of eZ Publish/Platform and most of the issues are inherited from Symfony Standard*.
Secondly we want to simplify upgrades a lot, and want to see if we can automate more of it for upgrades and updates.
* Upgrade conflicts on any distribution file user is invited to edit basically:
- Bundle inheritance to simplify bundle installs and upgrade
- composer.json - extends support
- multi kernel support to avoid upgrade conflicts on Kernel and enable multi site: EZP-22952 (See also App Layout: EZP-24265)
- upgrade conflicts on yml files
For web/app.php we solved it by having a generic one that is allowed to be extended, so should also find ways to solve the others in eZ Platform or in Symfony itself.