NO WAY!
as long as we have 5x5 AND 6x6 AND 7x7 as speedsolve events we can surely have 4BLD and 5BLD as blindfolded events...
This and make MBLD 10 minutes.
And even more NO WAY!!! That would ruin/change the whole event. MBLD is supposed to be the ultimate test of mind.
1. You need good concentration for the whole 60 minutes if you want to get good result (not easy)
2. You need good and fast memory with enough room for 20+ cubes if you want to be good at multi (not easy)
3. And you need fast and most of all RELIABLE execution to get good result at MBLD (also not easy)
For any other BLD event you need much shorter periods of time of full concentration. That's skill number 1 that MBLD needs that no other event does.
For any other BLD event you need much less memory space/locations. That's skill number 2 that MBLD needs that no other event does.
For any other BLD event you can just go fullspeed on execution since you have 3 attempts and only best one counts so you can DNF 2 and it doesn't affect your result. In MBLD it really really tests your accuracy also. That's skill number 3 that MBLD needs (well 4&5BLD need some degree of reliability but not nearly as much as MBLD).
If it was 10 minutes long ALL of those 3 skills would not be needed anymore and it would just be another 5BLD attempt with different (I would say even easier) execution.
If this is time issue then FMC mean of 3 takes 3 hours. MBLD takes 1 hour. And there are usually only few participants in MBLD so you can probably organize it simultaneously with some other event(s)...