You can do a lot of this with changing the appearance of spells or asking the DM to swap damage types (within reason- I don't see a big deal with a Frost Sphere over a Fireball, but a Sun Sphere or Thunderball might be a bit much). Even Hold Person could be momentarily freezing someone in a sheet of ice, etc. etc..
I've long wondered why D&D doesn't often support rules that let you do this without needing specialized subclasses/feats, whathave you, and the best I've come up with is it's about the IP. We expect to see spells like Burning Hands, Lightning Bolt, and Cone of Cold. If suddenly everyone was using Frost Fingers, Darkening Bolt, and Cone of Flame, maybe there would be a sense that you were playing a different game? That wouldn't bother me, but I know some people have strong feelings about "what D&D is/should be".
However, what really becomes an issue is what happens when you do have someone willing to try and be a specialist. In my Tales of the Valiant game, I have a Sorcerer who insists he's an Ice Sorcerer, using Metamagic to convert all of his spells to cold. This has caused issues when we fight things resistant to cold or vulnerable to the native element of a spell (like when we fought a monster vulnerable to fire, for example). He doesn't want to let go of his concept, even if it would be advantageous for him to do so, but this results in some fights where he starts plinking at enemies, not with magic, but a crossbow!