Unfortunately the class system the way it is and the fact that different spells have different potency with different mobs (or in other words, having just lighting type abilities would be very limiting on the types of mobs you could fight) means that this sort of combination would be pretty useless most of the time.
Hmmm but you can only have a few elemental type abilities on at any one time especially at lower levels... like I ended up putting a lot of points in lightning because I really only had enough AP to equip one nuke and since I was using shock spikes, loading up on lightning and equipping that nuke made sense. Also since you can't change skills/weapons in combat and there will be elemental themed weapons... people may actually benefit from specialization. Yeah, you won't be extra strong against things that have a resist on that element... so I would think about doing combos fire/ice or whatever so you at least are never totally gimped.
I guess what I am saying is people don't have to be maxed for every single situation... and in fact, they can't be. So your choice is to create a character that is balanced with all elements or to create a character that is specialized which will generally perform better than a balanced elemental affinity and sometimes perform worse. Since balanced is sort of boring I'm going to be specializing... and yeah you can restat but we all know that is a pain so it would only be worthwhile if you know ahead of time that you are going to be fighting a boss that resists your main element and switch up accordingly.
I'm probably going to be a storm mage (lightning and water affinity).
When it comes to sitting around not doing anything for long periods of time, only being active for short windows, and marginal changes and sidegrades I'd say FFXI players were the perfect choice for politicians.