1mana monsters

I'll concede that vanilla 1-mana creatures aren't needed for new players, but I still say that vanilla creatures in general are helpful to prevent some of them from being overwhelmed by too many choices at once. Magic uses vanilla creatures in starter games and core sets for the same reason. I guess if they're kept to the current beatsticks, and cards like Kelar Warrior that other cards care about, then there could be enough of them, but we can't really rule on this without hearing input from new players.

Anyway, I'm getting off topic. Back to the one-mana creatures.
I hadn't considered it before, since it wasn't touched upon beyond the first post or so, but I think you're right about chronology. I say that keywords are all we should make fit, since it's not really that obvious at a glance that certain additions to the code (such as abilities targetting creatures or players, or cards checking to see if they were damaged) were introduced in certain sets. The introduction of keywords, however, is set-defining, and I agree that these should be preserved.