Is it possible to make infusions and have them appear as an option in the main-class feature for it? I want to re-make the Many-handed pouch but I'm not very savvy with the homebrewing here.

It's not generally possible to add new options to existing feature sets like that via the homebrew system.  You can't do it for Maneuvers or Invocations, and I can't think of anything that would even come close to integrating into whatever new code it is they came up with for Infusions.

Bleh that's disappointing. I saw in a different section of the forum that custom Maneuvers and stuff is smth that's worked on? I hope that's (still) accurate, i'd like that.