If snafets is not fooling me (it could be out of date) keep the MLX-B without changing any omnipod: you will have a nice bonus to missile cooldown. You should play this build like a close range skirmisher. Keep your target in the sweetspot (120-200 meters for maximum damage or just 270 meters for the ATM-HE rounds optimal range) and enjoy dealing more damage per volley and DPS with 2xcATM3 than with a single SSRM6. If you can't poke, stick with your bigger brothers. 2 tons worth of ATM ammo will last 30 volleys (which means you can fire non-stop your ATMs for 2:30 minutes, slightly less than 2 minutes with quirks and skills), so IMHO there is no need for additional ammo because you are slow and very squishy for a brawlish skirmisher. I think it works best with enhanced UAVs (to keep the enemy positions up-to-date and maitain lock while breaking Line Of Sight) and artillery/air strikes to finish-off or soften your targets.
It's very particular and it was before or right while the MLX-G was becoming the new meta and most common build. It's hard to use and not very effective, but it will be fun to play in the right matches