There seems to be one thing I don't seem to be able to do and in my opinion would seem to be right in line with what you guys are trying to do (which seems to be to give us every form of rhythmic setup ever needed!) ;)
If each lane could have it's own overall division of bar that would allow for some very interesting polyrhythms overall.
Things like the top lane could be in (5/4) whilst lane 2 is in (7/8) and so forth with the other lanes if desired. All of them are basically then time "compressed" to fit within that one bar so they all start in the same place but 7 divisions would seem be faster than the 5 etc.
forgive me if it's already in there, just couldn't find it sorry and would really give us so many possibilities for sure! :)
Something like this crude example BUT if the triangles were the circles we have in Beat scholar and could be further segmented up as usual.
I did manage to recreate that beat by dividing up the lanes into segments of 3, 5 and 7 and then working out where the same beats would go but having lanes divided up separately into those and then still being able to divide up each segment on top of this would be polyrhythm heaven!