I mean, that was my strategy in the later Might and Magic games. Have the party fly and lob AOEs at groups of mobs. Its unsurprisingly really effective.Yeah, make the D&D spell feat Twin Spell a reality. This may resolve some of the caster's DPS concerns.
Also, make the spell (3rd level transmutation) Fly work for legendary, self-only. The spell Fly is iconic D&D spell, which any level 5 arcane spell caster can cast. Wait... make the up time depends on caster level and based on number of arcane lore. Make it not available for bards, artificers, alchemists.
That way, we can make stealth B-2 bombers (air support) in reality in DDO like in modern military. We don't see tanks or land-based military in real life launching a massive damage compared to bombers, why would we see it in fantasy? We only see land-based units to occupy.
In DDO, we have dragons, harpies, griffons and flying creatures that do not fly, we have goddess deities that can be engaged by melees, which is crazy.
I think it would either introduce mechanics issues in DDO, not be that useful (sewer quests), or be gam breaking depending on the quest.