It isn't too elegant a solution, but if you change the targeting filter when wielding and not wielding a weapon, you can also change between targeting enemies easily and allies easily on console especially if you also make use of the enemy list. Either that or add a hotkey or macro for the changing of targeting filter.

I personally don't think Supporter as a class or Job is a good idea(Aesthetically or from a game design standpoint), but I think the idea of supporter as a role(or a sub role of DPS) is an interesting direction for the game. I don't think this is something that should show much in 4 man dungeons, but I see a lot of potential for raid design. If this does become a thing and we see more classes or Jobs like Bard(who already receive a 20% damage penalty when using support skills), we need to make sure design is not dependent on the presence of these classes or jobs. Otherwise it would make queuing or building these raid parties harder.