Taking a break from SMTIV to play Project Cross Zone update: I ultimately gave up on trying to defeat T-elos in chapter 19 since three turns just isn't enough time to reach the center of the stage with more than Jin/Xiaoyu. You need at least three attackers to reach T-elos before she joins up with KOS-MOS and the western route is almost guaranteed to become a clusterfuck due to V-Dural blocking the route Harken/Kaguya need to take. And even if that did somehow work out, you'd still need a third team and the only units able to even draw close are Ryu/Ken and Reiji/Xiaomu, and due to the unfortunate choice support separation Vashyron isn't with this party for his +1 attack range skill and even Ryu/Ken's map attack is just one square shy of reaching T-elos by turn 3.
That said, I believe with the joining of KOS-MOS/T-elos, X/Zero, and Chris/Jill I should have every playable unit in the game. Now I just need to collect the rest of the supports having gained Alisa and Rikiya in the interim (incidentally, out of all the prologue characters only Bruno hasn't rejoined yet). Just beat chapter 21 which was interesting given that you're given a seize condition with a (still very generous) time limit and not very many characters to do it with compared to the usual team size.
Also nabbed me some Code of Princess for cheap earlier today and have started in on that. So far I'd say that $20 is almost about right, even if I've only scratched the surface so far.