Part of the reason for the design as is is to do as little “change the Warlock” as possible. That said, I kind-of had to give in to put shillelagh on their list, or force them to take human for a feat at first level.

For a true tinkering, putting martial weapon proficiencies with the various patrons is interesting. Could still have Pact of the Blade give all martials.

Having Eldritch Curse stop you from Hexing in the same round is not intentional, but I can’t think of a good way around it. I think making warlocks wait for 9th level for all three effects is a bit much. Dipping for 5 levels isn’t really a “dip” anymore, anyway, and is more a genuine investment.

Master of Hexes is almost redundant with making it a spell; the Warlock can just cast it again under most circumstances. I suppose an invocation that made it at will win a level requirement of 14 could work.