Let's say those DP remakes finally come out. Which Mythicals should have an ORAS Deoxys pulled on them and which ones should stay elusive and event-only?

Personally, I think Darkrai should have this done to it, seeing that its counterpart Cresselia is a Legendary Pokemon. Arceus as well, as a parallel to the unreleased event and summonable if the Creation trio is in the party.

Everyone else stays event-only.