I agree that some of the levels that have different targets or complications from the final level (or where the final level adds a target far from the others) could have different and quite interesting routes when compared to the final levels, but at the same time there would be a lot that are quite similar and wouldn't diverge much from what we already have.

On one hand, the more similar missions could probably be done in quick succession by someone going for the escalation as a whole, but on the other hand I would imagine it being a lot of work to set up since there's a ton of escalations and they often have a differing amount of levels each, on top of the fact that it might take awhile for the less inspiring levels to get more than a couple of runs posted.

Ultimately from my perspective I wouldn't be heartbroken or anything if they're not added right away and I tend to get into new levels pretty slowly (and even then I prefer to focus SA), but if they do get added I don't see why I wouldn't just go down the list of levels and get a time on each after learning the escalation's final level. The 1-X/all levels category could be an interesting approach to include the subsequent levels while avoiding the risk of site bloat/sparsely populated leaderboards.