Fanaelialae
Legend
My only objection is the gaming of the mechanics.Aside from aid and mage armor not being on the warlock spell list, I think they are interesting examples. If you dislike the chicken tactic, would you also be annoyed if the warlock cast those spells in the morning and then took a short rest to get back the slots? If so then it seems your issue is with the short rest mechanic, not the chicken. If not then I suspect it's a question of whether a chicken is a valid target. If the warlock snuck off before breakfast and killed a bear, would you have the same objection? Or maybe its this particular combination of gaming the targeting rules and the rest mechanic together?
I believe a warlock can use their slots to cast spells from other classes if they gain them via multi classing, so that is how they could cast mage armor or aid.
I've got no issues with pre casting hex (as I've stated before I'd allow it to be cast without a target). I've got no issues with a warlock short resting to regain spells. But the hex chicken is just someone trying to game the system, and that is terrible for immersion.