Jester David
Hero
If four arms were the main and coolest ability, sure. But thri-kreen usually had poison spitting and a standing jump ability as well.Honestly, WotC hasn't even proposed how they would do them, yet. Based on the MM block, though, being masters of two-weapon fighting seems legit, and being able to dual wield while using a shield doesn't seem overpowered compared to being a high dexterity Tortle dual-wielding with 20-22 AC naked.
Keeping the extra arms a little weaker leaves more room for other features.