New Gundam Breaker is fitting that bill for me. The gameplay is... not so good, to be polite, and it has what is possibly the WORST lock-on system ever devised in the history of automated targeting, which is insanely frustrating when you have to pick out a specific target in a group of nothing enemies. If you don't care much about Gundams or collection-based games, and don't have the patience to deal with mediocre arena fighter gameplay, then I can't recommend it.
But, it has 250 different Gundams and other mobile suits that you can freely mix and match parts and weapons between (at 1/144 and 1/100 scale even), not to mention a pretty damn good painting and weathering system. And I am a
huge mark for customization on this level, so that alone is enough to keep me entertained, either to make something actually cool looking or just put together some horrible kitbash nightmare and see how well it holds up.
I mean, you let me do something like this:
...and I'm going to be perfectly happy.