Expanding Limit Break System

[Nurvus]

SE will at some point need to step up their game where it comes to combat mechanics and build customization, as (in those areas) FFXIV is far behind most tab-targeting games (not counting animations and graphics).

No meaningful change or addition to the game will come without repercussions.
They just need to deal with it.

People make it sound like SE has a lot of trouble balancing things in this game, when in fact, the mechanics in this game are so linear they can't possibly be having any issue balancing things.

Your idea is Phantasy Star'ish, and not bad at all, and could work in unison.
Your idea could work by:
1 - Making personal Limit Breaks weaker
2 - Your multiplayer Limit Breaks become the "truly powerful", such as mass rez, reducing damage taken by everyone in the group, etc.