This is essentially focuspark's CN9-AL "Trident" build that has been modified to my liking on to the ENF-4R.
using Endo instead of Ferro, you can put in AMS and another JJ. or you could use a standard-Engine and a combination of ERLL and LL
Or just stick with the max STD engine... That gives you not only a shield arm, but an entire side torso too! 20% Cooldown 12.5% Range 12.5% Heat Gen 12.5% Duration Pretty damn good for a 3x LLas build! No need for XL with 47% cooling efficiency before quirks!