Well, in order to make LI something else than just CI (crappy Infantry

), it should have the advantages that it had historically :
- Loose formation, using more space, less affected by area fire and arrow volleys
- Bonuses when attacking from flank/rear - this should apply to all troops, but LI would benefit from their formation and speed to flank HI
- ABILITY TO REFUSE CLOSE COMBAT against heavier troops - this one is very important IMHO. For examples the role of Roman Velites was to fight enemy skirmishers, fire javelins on the enemy front ranks, and then retreat, not to engage Hannibal phalanx or elephants frontally

!
I'm not sure all this can be done without a serious overhaul of the combat/battle system, but as it stands now LI is quite hopeless ...