Am I right in thinking the Grenade Launcher Module grants 1 round of base attacks per M-point spent? Mark-14 has 5 Ranged base, so if you spend 1 M-point you can roll 5 base dice and push it? If you spend 2 M-points it is rolling the first attack of 5 with a push, then taking the second attack of a further 5 with a push? 3 or more M-points and you start getting insane numbers of dice. I'm not an expert of dice odds but in all likelihood as well as dealing damage you will also replenish the M-points spent. If you even spend 2-3 M-points it seems like a lot of damage, which will likely be put out every single turn as it usually replenishes the M-points spent.
The Four-Armed Mutation is the same but limited to close combat so less of a concern. The other damage-dealing powers don't tend to involve rolls so don't replenish M-points. Would it perhaps be better if the Grenade Launcher was like them and just caused the amount of damage equal to the M-point spend? Or maybe have it so you can't gain M-points from Mutation/Module attack rolls? I think the second solution is the most straightforward leaving it powerful and different from other powers but not something you can do every turn.