Could not disagree with you more there, especially if you want to do it on the cheap. You have essentially 3 valves types, one if you want to stay below 100 on it. You have about 3 body types if you don't want to run over 100. There isn't a lot to change out in terms of operating systems in a mag. There are really only a couple frame types that are bolt on, again, unless you want to spend a ton or mod the parts, which the OP again said he didn't want to do. They beauty of a mag IS it's simplicity. Most trained monkeys could build a mag with very little effort, and that's a positive in terms of design and function, not so much in terms of tinkering.
Mags do have a lot of options, but not many that are cheap and very little that are functionally different if you don't want to get into complexities of building a frame out, which is what the OP specifically mentioned. If you have any mechanical skill, a mag build should last about 30 minutes if you aren't going Pneu or EP on it. Keep in mind this is coming from someone who has built a pnuemag, Egomag, RT'ed mag, and shot one for about a decade. Again, fantastic engineering but not what the OP seemed to want in his postings.