maximum disk/ephemeral setting for the flavor to allow user to resize disks smaller

It would be a good feature to have a maximuim disk/ephemeral setting in the flavor, so you can resize down the ephemeral nova disks.
The user can either use the default (maximum), or go smaller.
This would be better than "0" special case Which is limited to admin.
The Admin can set the flavor no bigger than maximuim Disk/Ephemeral, to prevent over subscription.
This will reduce the N'th number of flavors for the NOVA ephemeral storage

nova boot --flavor c1.medium --image beab2327-f5a8-481a-8c0d-aba45cdf7184 \
--ephemeral size=50 \
--ephemeral size=100 \
--key-name key --nic net-id=89ce8949-2b6b-4418-8b3b-1773b191cbf9 \
INSTANCE1

| ID | Name | RAM | Disk | Ephemeral | VCPUs | Is Public |
+----+-----------------+-------+------+-----------+-------+-----------+
| 10 | c1.medium | 16384 | 80 | 250 | 8 | True |
| 2 | m1.medium | 8192 | 80 | 0 | 2 | True |
| 22 | m1.extra_normal | 1024 | 0 | 0 | 1 | True |
+----+-----------------+-------+------+-----------+-------+-----------+