Figured I run them as 'counts as' GK Paladins, as the statline feels about right for the Thunder Warrior fluff (psychic powers counting as early transhuman proto-geneseed manipulations). Going to eventually convert up another five; one to be the squad leader, the other four with modified Heavy Bolters to count as Psycannon.
On a side note: what lovely models the Stormcast Eternals are. What lovely, lovely models.