Implement "common mods", includeable from
  {$user,$share}/games/common/$modname
by using the game.conf setting
  common_mods = $modname,$modname2,...

Also add a menuheader, menusplash, menufooter_clouds, and allow HD menu footers.
And finally don't git-ignore textures/base/.

Remerge some files in order to reduce number of additional files

Make necessary changes for split, rename files, reorganize some bits