after a quick shower thinking about the best way to do this, I came up with this idea that I hope you like and modify to your liking:

Change the preomnor to give no food need or make the metabolism so huge that they can go for at least a month without eating.. (astartes usually eat human food just for the sake of eat or if nothing else is available, but they can definitely take every single nutritious molecule out of it and use it)

Then, give them a need for "astartes nutrient pack", using the same mechanism as addictions, you can give a need that progresses over a long ass time, Id go for at least 6 months, and the different stages of it reduce the healing factor of the astartes, with the last, reducing their consciousness so that they go into their metabolic coma..

That Astartes nutrient pack should have the 2 things they need that no other human do, their special kind of proteins and ceramite (seriously, these dude EAT ceramite for their bones...), how to make an astartes nutrient pack?

100 plasteel, 50 stone blocks, on the smithy gives ceramite. 500 meat and 25 neutramine on chemistry or medic workstation give you Astartes Protein Powder, mix them up in cook station and youve got your "meal" (which will work as a drug resetting their need and MAYBE giving them a good thought like "ready for war" or some ♥♥♥♥ like that)

This way we fix both problems at the same time, keep it lore friendly but still have the difficulty of their very specific required diet, even if it is once in a blue moon...

Also, while we are talking about health tab and drugs, they should be immune to drugs in general, nothing affecting a normal human and not killing him would work on an astartes, they would filter out wake-up like water.. In fact, not even luciferium should work on them as their biological makeup is vastly different to what the nanites were programmed to work with

Of course I'm trying to make this all work under the constraints of the game so that there is no C coding needed, but a better way of doing this would be to make a need need for astartes that replaces food with "nutrition", which is kinda different, and that need to only be able to be solved with this pack.. Which should only be able to be ingested by astartes (and definitely kill any human that tries it, after all this does have ceramite in it)