In my opinion, the best balance would be to bring back a veteran of the franchise, like Sam Hulick or Jack Wall, and then surround them with some fresh blood: composers new to the franchise. That way, you can keep some of the original Mass Effect identity, but can also make it fresh, appropriate for a fresh start for the franchise.
Some composers who can be good for MEA: Jesper Kyd, Lorne Balfe, even Trevor Morris could work.
If we go for heavy weights, Hans Zimmer or Jeremy Soule would be fantastic. Zimmer's resume speaks for itself, and he can pull off great space soundtracks like in Interstellar. Soule has worked for Bioware in the past on KOTOR, and his ambient soundtracks both in KOTOR and Skyrim are fantastic, perfect for exploring new planets.
Ideally, we would target a soundtrack that's a mixture of Interstellar's and Skyrim's awe and wonder inspiring moments, all mixed with a Mass Effect sound. Throw is some synth for good mesure, and we would be set