bnm81002 said:
ok to be clear, I can install rev19 with 37 base for the music games, 57 base for the other games and 38 base for HBC apps, so I can install 3 different bases?
No. You can install two through very round-about methods (install one base, copy one IOS to WAD, install other base, install WAD of original base) but you can't have all three.
Fortunately, it seems the only apps that won't work with rev 19 are those that need ES Identify, and those are pretty much only for WAD installs and so on. Most of those apps allow you to choose an IOS and you can just choose 222 as it has ES Identify. Thus, two versions of 249 is enough to get everything.
Personally, I'd forgo the trouble of multiple installs and uninstalls and just go with the following (unspecified IOSes don't matter):
IOS249 rev 19 base 57 (for most games)
IOS222 v5 base 38 (for installation apps)
IOS223 v4 38+37 (select in per-game options for music games)
That's probably the best compatibility setup you can have. If you have a bit more patience to do the WAD installations of IOS249, then this might be best:
IOS249 rev 19 base 38 (for installation apps)
IOS250 rev 19 base 57 (with ios=250 in config.txt for most games)
IOS223 v4 38+37 (select in per-game options for music games)