What follows is mainly for me, but maybe it is useful.
I would view list-PR adoption as an ‘insulating’ action by a coalition that is hard but not impossible to put together. The same would go for national/widespread imposition of ballot fusion (also see first link).
I am wary of efforts to promote PR for its own sake.
I think we are going to see (or at least hear about) more reform activity than usual in cities and maybe some states. It would be nice to see this go in the “more parties” direction.
I prefer to say “pro-party.” I don’t think that direction has to alter the party system by, say, causing lots of parties to win seats in Congress or run presidential candidates.
Even locally, I am reluctant to say it would be easy to build a pro-party reform coalition.