Magic Missile is one of the topics that gets thrown around the Dragonsfoot Classic D&D pages (and I assume the AD&D pages as well, although I rarely read them) quite often. It's up there with demi-human level limits and alignment as far as perennial hot topics go.
Anyway, this was a waking up too early and lying in bed thought I had this morning.
Mentzer D&D has a discrepancy in the Magic Missile spell. The actual spell description lists a duration of 1 Round. The spell list reference sheet from the middle of the players' book lists a duration of 1 Turn.
Much discussion has been made on DF about the ability to cast MM BEFORE going into an encounter to have it "prepped" and in fact being able to cast it multiple times (and at higher levels getting multiple missiles per casting) and being able to one-hit almost any creature.
I'm not going to discuss that, but my idea was connected to the 1 Turn error (if it is indeed in error). I was thinking of the possibility of using a 1 Turn duration (so one encounter/battle) per casting, with a missile (or missiles) being available to be shot every Round while the spell lasts, as long as no other spell is being cast that Round.
The kicker is, I'd use the Holmes (and Greyhawk expansion?) rule that the M-U needs to roll to hit with each missile - which acts like a +1 magical arrow.
It would give a bit more oomph to MM at low levels, but with a 36 level Mentzer BECM spread, would definitely be too powerful at the high levels. Well, the rate and number of extra missiles could be slowed, a Moldvay/Cook cap of level 14 could be in place, or the extra missiles thing could just be scrapped altogether.
Anyway, it would be an interesting way to run it I think.