I've read fics where Tal ends up with Billy. And I don't know why. So as long as you can justify OC/Tal then go for it!
You shouldn't be too worried about doing an OC. Voyager had ~150 personel but on screen was on 20 30 tops.
If you're still really worried after you have gone into the character's background, then perhaps you could post a sample here and let the board decide?