i have not tried it, but /targetenemy (or /tenemy) is a text command wich targets the closest enemy in your range.
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First two paragraphs are what I do. It's weird at first but I've done weirder in other games. Alternatively you could rebind r2 to l1 and vice versa; using the left shoulder buttons as toggles and the right shoulder buttons as actions a la WoW's controller mod, however for XIV it may not be as feasible due to how many more buttons on average XIV uses compared to WoW.
Macros really are the best option. However all Combat abilities can be fit on 2 hotbars for most jobs.
I use 3 hotbars and that is viable, especially once muscle memory comes into place.
Thanks again for all the replies - the double tap configuration works pretty well; gives me eight additional skill sets tied to the right side/buttons so moving around and attacking is still pretty fluid.