Well, firstly, the whole point is that you sacrifice warlock slots because they come back on a short rest, if you're sacrificing sorcerer slots you're not gaining anything and might as well be a pure sorcerer.See, if the Player was spending Sorcerer points (and maybe sacrificing Sorcerer spell slots) to renew Warlock slots, I might be more lenient. But I have yet to see that happen.
And secondly, the reaction to the Coffeelock is much like the initial reaction to the 3e warlock: "Oh noes, it gets bazillions of castings of weak spells, that must be overpowered (if you completely ignore the highly limited spells known and low power level of the spells available)!" On a cheese scale of soft brie to sharp cheddar, it barely rates as Velveeta.
I mean, personally, I prefer to chuck it entirely in favor of a more 3e-like version, where you have basically no usage restrictions on your magic, you can modify your primary attack in lots of ways, and Eldritch Blast isn't just a cantrip that all the other casters take with Magic Initiate and make the warlock sad, so I'm not the best one to ask about that.Got any ideas on boosts to just Warlocks?