It'd be neat if Maxwell could use the Codex Umbra to summon minions to do general work in an area of his choosing instead of summoning minions that can only do specific tasks.
For example he would equip the Codex Umbra in a similar way to to the forge's petrifying books and cast an aoe onto an area that he would want worked on. (Ideally with a considerably shorter cast time) A shadow minion would pop out from Maxwell and collect resources, dig things up, pickup items and so on and so forth. Once the tasks in the area have been completed the minion will go back to Maxwell with whatever has been collected and then an amount of fuel is deducted from the Codex Umbra (Which would be recharged with nightmare fuel) depending on how much work was completed. The minion could be stopped by punching it like the current version deducting however much fuel it had used up at that point.
If he wanted his shadow minions to fight he would instead equip the Codex Umbra and direct an attack at range to summon a shadow hit man to murder the subject. Whether or not the fighter minions would be stronger or not I am not totally sure, it would be interesting to have them draw aggro better and tank some hits but otherwise that is up for debate. The limit of how many minions he could summon at a time would probably be about the same as it is currently as well as taking parts of his sanity in exchange for the work.
This would make his kit into a much more unique taskmaster kind of character instead of the forest killing shadow gang he is right now. It would nerf his ability to completely decimate forests/rock biomes (Which means Woodie would be the best woodcutter now) in exchange for more options with his minions. The kit makes sense with his character and would fill the fast gatherer niche that is absent from the current lineup.
Well that's all i've got to say on the subject. If you've got some feedback on the idea I would love to hear it.