The first thing a JK really needs is an evap canister skid plate - or a relocation of that evap canister.
Second thing on my list for underneath a JK would be diff covers.
After that, I would aim at either an up-armored oil pan, or a full belly skid plate system....to be honest the JK's seem to have the little minivan engine tucked up fairly high, and despite extensive "use" of the fuel tank skid plate on my JKU due to the poor breakover angle I have not felt the need to add anything other than diff covers and the evap canister skid.
All of that experience is with the old 3.8 - I can't offer any specific guidance on the new pentastar.