Derp? I already answered your question. If a group only expects a Red Mage to Haste/Cure/Refresh, then either the group is made up of terrible players, or the group knows that the Red Mage is a terrible player who would be unable to do more than that anyways. Only terrible, terrible Red Mages are limited to Haste/Refresh/Cures.
Honestly, I see absolutely no reason to start nerfing Red Mage's spell selection just so that people have a "reason" to melee. What you're asking for is an excuse. "Sorry guys, I can't use the enfeeble you want unless I'm hitting it with a sword ^_^". That, or the enfeeble granted by melee'ing is useless, in which case it does nothing for you. Do you see the dilemma here?
Would I mind having a "Boost attack/acc" and "Boost Mag Acc/Mag Attack" stance option? Naw. But messing with spell selection is just asking for trouble.