The maps can be done without Lilac, but you'd have to tailor the squads to specific speeds, which might have to be quite extreme on ?-6 and ?-7. I'm only eyeballing, but I'd say, above 700 for the fast squads and just below 400 for the slow ones.
Customizing to such extreme speeds would for most people involve mixing in some units that they hardly improved, like a couple of 2* or 3* girls, which in turn might make it hard to get past the bosses, or even past some of the pests. Really, how many people have evolved 2* girls? Some people even got rid of their 2* girls, evolved or not, to preserve space for 5* ones. I almost feel sorry for them for when nation battles start, since they'll have to upgrade the girls they got rid of again, to get some full squads that actually survive their first encounter. Well, I don't really feel sorry for them, since they made the decision themselves to use the necessary flowergems on a gamble for some 5-6* girls, which they may or may not have gotten because of it.