It strikes me that (as a driver) to increase capacity then you need to apply variable speed limits in the same way that you do for arrivals. ie. for the first a/c in a bunch give him a min 320 knots and progressively less for the rest. Most drivers that I know wouldn't have a problem with this (conditions permiting of course) and it would achieve the aim i.e. to avoid bunching.
Having a fixed speed limit for most (ATRs and DC10's/Jumbos excepting) just delays the problem till later, coz the second you get above FL100 the everyone is at a different speed.
Thats just me thinking about it anyhow. Would love to hear how its actually going...
ooh just thought. Many A/C have bird speed limits which may limit things below FL80...