The wife and I have Volquartsen triggers and the modified bolt release (allows you to slingshot instead of having to use two fingers) on our 10/22. You said precision-ish trainer, so I would focus on getting the rifle as close to the center fire you are training for as possible. Same or very similar stock, same glass or at least same reticle/power/eye relief.

the problem with sub caliber trainers is that you will end up being disappointed with the accuracy. If you spend the cash on a new barrel make sure you invest in quality hi velocity ammo, most like CCI stuff.

i get 4 MOA from my 10/22 out to about 100m with tech sights (peep rear sight that attaches to Reciever for longer sight radius) and bulk pack ammo, shooting in field positions. Neither of us shoot much with optics, and only own one rifle with a magnified optic, so this works for us.

what rifle are you trying to use it as a stand in for?