Need a couple conversion suggestions

[FunWithFire]

So my brother has decided to start getting into arcade games as well. But he is the "purchase first, research last" type of guy.
His first purchase was a Bottom of the Ninth game that was in actually very nice condition for a pretty good price. It looks as if it was converted though, from something else. Problem with this one is that he is just not really a fan of the game.
His second purchase was a NFL Blitz 2000 Gold 4 player. This is a nice looking game as well, and the problem with this one is that he wanted to convert it into a NFL Blitz/NBA on NBC. After maybe 5 minutes of research, I learned that it is a completely different boardset needed for the duel game.
So now the dilemma. He wants to do something with these cabs, and having very little experience with this stuff, I figured I would ask you guys. The Bottom of the Ninth is a JAMMA game, so that isn't so bad. I would just have to find something else that is a horizontal, 2 button game. Except he has been reading about the Nintendo Playchoice 10's and now wants to do something like that. Is that even feasible? Would I have to replace the whole Jamma harness to put in the Playchoice?
The NFL Blitz is a different situation all-together. If it was a showcase cab, it could make for a nice shooter, but that is nt the case. That one I just have no idea what to do. So if you guys have any suggestions, or have done something similar in the past, I am all ears.