I think you seriously fail to realize how little people care about the 30min penalty - people did it all the time pre-Praetorium /Castrum rework because people wanted to fish for Prae and 30mins was literally nothing. Or how the moment an extreme shows up in mentor roulette, you usually have some people bail. They'll queue at full ilvl so their reward is guaranteed to be maxed, then leave if its not an easy one. You aren't punishing them in the slightest, as much as you want to want to believe otherwise. Also like I said, it only affects the first person to leave. The rest of the people who were hoping for CT in the raid get a free out and zero punishment.
You also fail to realize that outside of tanks, the queue for alliance is only like 5mins long. a NIER raid can be 40mins. It'd literally be faster to drop the raid, re-queue and bank on literally anything else popping, since even with a re-queue + clear time of say, Srycus, it's still only 20mins, compared to NIER's double that.
Again, your idea has literally no affect on the people you want it to have an affect on. Cheesers will just queue at max ilvl instead for max reward, then leave if they don't like it since 30mins is literally nothing as a punishment, all because statistically, even with ilvl cheese negated, you're still likely to get CT 80% of the time anyway due to ilvl cheesing being such a minor issue compared to the other 5 factors all heavily biasing CT in the roulette and its a safe gamble to make. The only people your idea hurts at all are the innocent who have to deal with leavers, no matter how easy or uneasy it may be to re-fill their ranks. Even doubly so if its late at night and certain roles can be harder to find.
Except they can't guarantee void ark, and Mhach would be a potential option since you can only queue for a roulette if you qualify for at least 2 instances, which would be a far cry from the ilvl cheese of CT/Srycus guaranteeing 2 ultra easy instances. Your statement also implies those people are willing to do 2 alliance raid roulettes a day, when most people I've heard from who ilvl cheese have varying degrees of 'I do it because I have limited playtime and want a quick instance'.
Plus, unlike CT that is forced mandatory for every player, ilvl cheese will have a much lesser impact on the non-CT roulette by virtue of what people has unlocked will play a much bigger role since everything is optional. If even one person you get matched with doesn't have Void Ark unlocked, you won't be seeing it.
People can try and 5000 iq play with their ideas all they want, but Occam's Razor is at play here. Especially when you factor in the fact the devs don't care about ilvl cheesing, since CT is the only raid series that is required by story and thus, are the only queues they want to make sure are constantly filled for new players. If they do any solution, they'll go with the easiest one; just make it its own roulette since its the least amount of time on their end, instead of having to create some complex system that will still be exploited easily anyhow.