Cons to your second and third option: lack of transparency to player leading to situations where people are confused why they're blocked when they meet minimum ilevel.

The only additional ilevel requirement I would add is a minimum main hand (and offhand for Paladin) requirement.

And add tiered ilevel requirements for alliance roulette based on the highest raid you could have access to so people can't cheese the queue to Crystal Tower as much. E.g. if you're level 70 you have to meet the level 70 alliance ilevel to queue for the roulette regardless of whether you unlocked the raid. They'd still be able to not unlock the later raids to force CT, but at least they couldn't do it by equipping a bunch of ironworks, or worse.