You can sort of do whatever with those characters, they're all good in any position on a team and they all have good assists. Honestly you could pick the team in any order and use either of the default assists for all three characters and you'd end up with a good team.
Gun to my head, I guess... Fukua (H Drill) / Bella (Cerecopter) / Eliza (Dive of Horus)? Dive of Horus gives you an overhead assist that can also make your setups safe. Cerecopter gives you a lockdown assist, it's also particularly useful for Fukua since it lets her convert off her air grab, which she can't normally do. (Eliza's H Spiral assist can do the same thing, but Cerecopter assist and Spiral assist on the same team would be redundant). IDK what your other characters get off these assists but they're all pretty solid assists so I'm sure it'll work out.