I'd go with tech marine for Primaris or a Heresy style Primaris support unit.
Thing is though following the current all the same weapon trend do Primaris need an entire squad of flamers or could it be a single special weapons option as a squad upgrade?
Yeah, we're at the point where I hope that the inevitable Primaris wave 2 includes an upgrade sprue for the actual Intercessor squad, instead of the Intercessor sergeants getting all of the options. Ideally they'd even pack that sprue in with the base Intercessor kit going forward.
But such a kit would have a flamer or two along with a mess of chainswords and a few other weapons options.
Edited by Lord Nord, 08 January 2019 - 03:36 PM.