I won't even begin to point out the absurdity of one day ladders as igiveuponaname has done this well enough.
I'm pretty happy with Tb0lt's current suggestion but I also want to add:
That's my reasoning for why I think having the spotlight ladder still lasting for a month is still the most viable option. Does it tend to overstay its welcome? Sure. But I think for these types of tiers, especially if they are going to be available once a year, you would much rather have a tier overstay its welcome than have them feel as though their stay was cut short. The community will play their games regardless of whether or not there is a ladder; the ladder is for the new players that the community wishes to attract.
I agree with all of this. Better to have a format stick around for an entire month and give it the maximum amount of possible eyes on it, than to rush spotlight ladders to exist every 2 weeks.
The goal of having an actual featured metagame every month is to try and give it the maximum amount of opportunity. Having a spotlight win out means we normally run one(or two) roomtours for it a day, there's an on demand ladder(which I admit can vary in terms of activity based on time of day + overall player interest), and you have a spotlight round robin tour which basically means you're getting 4 bo3 sets for fun(assuming someone doesn't drop out or no show).
If we switch to super accelerated ladders just for the sake of "fairness," we aren't actually accomplishing anything beyond dangling a format in front of a playerbase's face before taking it away. And frankly, as skitty said, the mains will continue to think about their format whether or not a tier is ladderable. The goal is really to try and appeal to more casual-minded players who might just get hooked and become a fresh new talent for said community. We stand to gain more from having 4 week ladders on that end.
The only "fairness" that should be considered is how long of a cooldown a format has such that other communities have their chance to win out on a ladder, and that's covered in the current proposal. So I personally don't have any complaints, but if I do think of something I'll either edit this or create a separate post.
The last thing I will add: you can always ask RoA staff for tours in the room for the formats you're interested in, even if they aren't spotlight formats! Asking for friendlies or a roomtour is always encouraged, even if staff may not always be available or interested in doing the latter. It's what the room is here for.