How to fix this IK rig?

I have the ALSV4 community replicated.
Onto that the PolygonFantasyKingdom set.

Basically i see my problem as following:


The arms of the added character are longer. Upper and lowerarm.
Even angleing the arms more just ends up more messy.
Atm i see as only solution to get into blender and “shorten” the lower and upperarm of my newly added modells.

Any other solution ideas?