Hmm, looking through vertical mame games in .73 (what I have installed at the moment).
I find you basically have Centipede, Millipede, Quantum, Bowling (assorted), Golf (assorted), and American Horseshoes using a trackball. I cannot off hand think of any horizontal trackball titles that would be acceptable with aspect ratio squashed to vertical.
While you have dozens of assorted arkanoid rip offs, Tempest, Break Out, Bomb Bee (and sequels), Kick-Man, several playable driving games, and a few more obscure vector titles. There are also a small number of horizontal spinner titles that would be acceptable squashed to vertical, Avalanche, several arkanoid rip offs, possibly most horizontal vector spinner titles.