So, with each spell list, which Invocations would you pick, and why?
Umm... Arcane Swordsage.
Really?
[spoiler]
SpellsWhat does a Ranger get that is so great? Hunter's Eye. UMD it.
What does a Paladin get that is so great? Nothing.
What does a Hexblade get that is so great? It's not spells.
Since each of those classes top out at 4th level spells. You can buy wands of their spells and cast them as a Warlock with your class skill Use Magic Device abilities while still maintaining your sort-of exclusive spell-like list.
Class FeaturesSmite Evil sucks, use a Crusader's strike, Hellreaver's Exalted Smite, or combo with Charging Smite in which case Smite takes a backseat anyway.
Favored Enemy is too campaign exclusive, retraining opens up a possibility but not at the cost of the Warlock's SLAs.
And the Curse would be better if intimidate didn't out shine it and, you know, it didn't suck.
InvocationsWhile the list is tiny you get things like Summon Swarm to rape low level fights while you FLEE. Later on you'll pick up things like Flight, Charm monster, Black Tentacles, Save-or-Dies, Eldritch Glaive's damage rape (yes, blast shapes are warlock invocations), etc. Also there is a coolness factor in the warlock's invocations like having the option to rip off your hand and throw it at someone to deal 1d6 Charisma damage while changing your appearance to look like them (before you made them ugly).
[/spoiler]
So in the end. My first step to optimizing your pondering would be not to use it.
The problem lies in the crap abilities the Paladin/Hexblade/Ranger get, the ease of replication of spells, and of course the fact that the SLAs while generally poor have a few gems (and one gold house named Glaive) that are just not worth giving up. Of course, choosing to play as a weak class without it's only redeemable trait in exchange to mimic an already weak class only without ANY of their redeemable traits is probably a tall tell sign into it's self.