I think these 4 might be my best options, but honestly, I have issues with just about all of them.

FSG- I love this unit and all, but I feel like LSV alone invalidates his existence. At 4 stars, his tanking's non-existent, his color is at a terrible spot, and the fact that he's ranged goes against this super strike oriented duo. However, once lsv is out of the picture, then his strengths become far more apparent. The endurance null is really nice on units like kid Buu, his green card can make him a pseudo sniper, and the support from his gauge is nice too. But I feel like LSV alone makes it really hard to justify him.

LF Future Gohan- Definitely one of my favorite units in the game for sure. In theory, he's a great 3rd option. He can support lsv and fsk with buff deletion, his color is excellent at tanking lsv, and Buuhan isn't really an issue thanks to the fact that fsk eats Buuhans for breakfast (mostly). The main problem tho is that his damage is super low, and his tanking isn't impressive by today's standards.

LF Gotenks- Okay, ik I'm probably gonna lose people with this, but I CAN somewhat see the potential. His green card spam is really nice since it means fsk post-revive will have more aoe greens to spam, and he gives LSV more green cards to spam as well. He can also counteract Buuhan's gauge since Gotenks's gauge can seal blue cards, removing Buuhan's only way of punishing me for activating his gauge. However, at this low stars, his tanking is atrocious, the damage is kinda alright, and he's kind of a featured boost merchant. Once he leaves, he'll likely go right back to irrelevancy.

Transforming Gotenks- Not much to say with this guy. Super strong blue cards, but that's about it. He does allow more flexibility in my benches, allowing to zenkai buff lsv (LF sv isn't at 14 stars), but the limited transformation and the fact that he's kind of a blue card merchant makes me kinda hesitant.

What do y'all think? Maybe there are other units I'm not considering? Maybe someone like the ROF Blues or Evoken or Hitku can also work, but they don't really synergize with this duo well at all imo.

In your opinion, who's the best 3rd option to pair with these two?