On the actual map, next to the fleet symbol, I think it would be useful to have next to the fleet marker a 2 digit number showing how much delta v is left in the fleet, and besides a number showing how much delta v was spent last turn.
So, for example, you would have something like below:
So, next to the fleet symbol, the 5.6 would be how much delta v (in km/s) is remaining, and the (1.0) says that it burned 1.0 km/s last turn. I think this should be visable on both friendly and enemy fleets: it should be relatively easy enough with basic survailance to determine how much delta v an enemy fleet has left, and how much of a change in velocity a fleet has burned. This would be especially useful in missile and other intercept dodging to see how much delta v is being expended on dodging.