Another vote for the 10/22. Get the basic carbine, shoot it for a while, and then see what, if any, changes you want to make to it. The design is brilliantly simple -- anyone with reasonable mechanical ability should be able to work on one -- and aftermarket parts are available to set it up and/or upgrade it however you want. The most bang for the buck, IMO, is a
trigger job or aftermarket trigger group parts.
As far as the mag release goes, on newer models, it's fine. With minimal practice, you can easily change mags one-handed.