IDK if SE would seriously consider this system....it could have the potential for additional congestion server-side that they don't want to get into. If they set it up with a bit-mask concept like the NPC/Moogle storage, it might not be too big a deal (but you'd certainly not be able to do augmented items, possibly other items too depeding on how long the DWORD can be on the legacy code/systems involved). But if it were to be designed as custom views of your avatar's database tables, it might introduce a new wave of traffic (people tweaking the macros, then using them) that might very well increase the load/lag to the servers.

We've all seen them use increased lag as an excuse before....probably would come up with this idea as well.