I'd also love to be able to merge duplicate opportunities or even projects

I, also, need a way to mass archive because of the number of leads I receive. Preferably, the method could also be automated.

Definitely mass archive! I like keeping a historical record of what has come before, but getting them off the initial filter is super helpful!

(Reminder our use case is that we use opportunities for novel/short story submissions, so we filter hundreds through at any one time.)