I made my own Mario Party roster concept art I went by the Super Mario Party and Super Mario Party Jamboree approach and did a 30 character roster as Super has 20 and Jamboree has 22 and the new one will be on Switch 2 so 30 characters doesn't seem too far fetched
with 6 unlockables as Mario Party has had unlockables since at least Mario Party 8 I'll post my full character roster in a few days