So far I have 8 players
I would suggest a 7 round RR with two rounds per week (one round per week seems too slow for me). Play 4 games (base, echoes, e/f, e/f/c), defaulting to standard achievement target (but you can play extra achievement if you both agree). Ranking by number of matches (=4 games) won, with number of games won as tiebreaker.
If no one objects to the format within 24hr, I will create a Challonge bracket with these entries plus whoever posts there before then and send out assignments.