I have to say I disagree about not giving the DM your opinions about a game world where the group haven't even begun play yet - and in this particular case, OGB ASKED me for my feedback - so he can't really complain when he gets it!! Anyway I think the ref DOES have to consider player preferences - he has to at least offer the players a world that they can believe in, characters that they can believe in, characters that they can get excited about playing. Otherwise they either won't play, or will play but won't enjoy it - neither of which can possibly be a desired outcome. No-one has the God-given right to be the group's DM / ref / GM - especially in a group with 3+ potential refs.
Fair enough. But there are two basic points here.
1) Wizards deserve armor. This is a balance issue and while we can offer some opinions here, this is basically all OGB's decision.
2) Wizards should be able to wear armor. This is a world building question. Most people seem to agree this is generally true, but not everyone thinks so, and I think just about everyone agrees that in some scenarios, wizards would not be able to wear armor. I think there is a very good argument for saying somatic components = you can't wear armor is sort of implausible. But if that is the case, you still have to at least consider any balance problems. And by "you" I mean, "Basically, the GM with some input from the players."
Let's say you win argument 2) but lose argument 1). It's within your GM's purview to come up another explanation, whether it's the conductivity of materials (Rolemaster), magic generating heat (Scarred Lands), or special vows (Krynn).
As a veteran Talislanta player, I can say that allowing full plate for wizards is not usually a problem. In D&D, you are looking at a reduced movement rate, plus either thee feats or one level of fighter or cleric just to get proficiency, which you need to eliminate attack roll penalties (which, by the way, would include rays and touch spells). Even if it were totally allowed, as a player, I would be looking at bracers, which a a side benefit protect against incorporeal attacks and certain touch attacks. Also, casting mage armor and carrying around scrolls of magic missile works out to be a fairly cheap option in the long run compared to mithril chain shirts and the like.