Might consider it after revisiting Hospital outpost, due to similarity. The main issue that comes from original VOE is that you can put amount of items per skill and it must be int (so even 1 item per 2 skill not possible). There is no really a good way to patch it, but I might know a way for making it work for my outposts.
Alternatively you can also just open VOE folder and find Def for Outpost_Production, where you can add whatever item you need it to produce. But once again you limited by amount per 1 skill, so you will need to end up with min 20 HE per 20 skill.

Ah, that's unfortunate, the use of an integer there really puts a limit on higher-value outputs. Have you considered compensating for it with frequency? I'm not sure if Hospital counts as a different kind of outpost or is it sill a production one under the hood and any settings are shared between different production outpost types. If it's different and you can control how often it produces separately from the other production outposts, then making it deliver on an annual cadence would probably give enough room to support HE shells in integer, even if AG is still out of the question.