@Firebrand
There's an idea. The only reason I'm wary about that is that it leaves a good chunk of interaction with one's self. Of course, instead of just role-playing the development of one character through their trials, this lets players develop a relationship, seeing how two strangers who are forced to work together deal with the Reapers' Game. Of course, inter-team interaction would still exist; some foes would be too great for one pair to defeat alone, etc. It's a great idea, really, thanks.
I don't know about the archetypes though. Character personalities should be up to the players, and if they want to take inspiration from something like Jungian archetypes, that's their prerogative, but I wouldn't require it. Compared to other character "splats" like Tarot Arcana (in a Persona game), which have a fair degree of interpretation despite the character types, the archetypes seem to be a little narrower.
Right, player to player interaction could still happen, but it would encourage people with good writing skills who have long-term goals for their characters to join because they wouldn't necessarily be limited to what developments they could bring out by interactions solely with other characters. There could be more introspective elements as well, plus P-vs.-P things would be even more interesting because it's not like a player will be screwing over someone they allied with just a few challenges ago. They could really be ruthlessly in it to win it.
And I only proposed the archetype thing because it would ensure that people would enlist with two distinctly different characters, because the whole point of the Reaper Game is to connect with someone not like you and overcome challenges together. It's just a bit more lax than saying "Okay, so you have one character who is a kindhearted but closed-off introvert, so your other character must be a cynical extrovert who always speaks their mind". Not saying Jungian archetypes or even any other character framework is the best way to go, but imo it's one of the easier templates to use and to juxtapose with. Ultimately, it really doesn't matter how you do it, but I think that RP would be best if each player controlled two characters. It's not even like that would be too far a stretch because, like I said yesterday, TWEWY is a game where you control two people simultaneously.