Horus Heresy Emperor's Children

I inherited a very small army of Emperor's Children for Horus Heresy which I had commission painted for him several years ago (that's actually the reason I got it for free). It wasn't really playable or a proper army, with a 10-man Mk4 squad and 10 more resin Emperor's Children Mk4 shoulder pads, a 5-man Tartaros terminator squad, an old Emperor's Children dreadnought with some new-in-packaging resin arms, and Saul Tarvitz. I bought more Mk4 marines to use up the shoulder pads and make the list (nearly) legal, more Tartaros terminators - 2 of the painted ones were built in ways I didn't find useful so I used 2 of the new ones to replace them, then used 5 more to make a second squad which made the army fully legal to play if still small - and transfers to replace the symbols I painted onto them originally. I'm not sure what if anything to get for them next, I've considered dreadnoughts, more infantry, tanks, and even Palatine Blades. And I really like the idea of them being loyalists with white shoulder pad insets instead of purple, but I don't know if it'll be as good as I want/imagine it to be. I like the idea of a loyalist force under Saul Tarvitz made up mostly of the 10th company which he leads/led (in the story he dies) and the resin dreadnought will become Ancient Rylanor.

Thanks for reading/listening. I think I just need to paint the ones I've got first.