you can only set the names of the hcs to "game speed: fast"

Play them online.

Sir Hans , explain better please. I have to rename home city file?

There is a homecity editor in the editor where you can change the hc cards and the hc names. I thought you know it.

@Hans: Kingor wants to change the actual game speed, not production times. You know how when you're testing a scenario it will be normal speed where as you can play a skirmish game and it's Fast? He wants to make his created scenarios as fast as Skirmish games.

@Kingor: I'm not sure of any way to do this, sorry. I would also like to speed my custom Scenarios' game speeds up.

In AoM's "game.con" the following commands are listed:
map ("shift-g", "developer", "gameSpeedMult(2.0)")
map ("control-shift-g", "developer", "gameSpeedMult(0.5)")
I don't know whether it works also outside developer mode, nor inside AoE3.

For testing in AoE3 you had to add the lines in "user.con" and replace "developer" with "game", maybe "world".
If it works, the command "gameSpeedMult(...)" could be placed also in a trigger effect.
Try out and report

@Hans: Kingor wants to change the actual game speed, not production times. You know how when you're testing a scenario it will be normal speed where as you can play a skirmish game and it's Fast? He wants to make his created scenarios as fast as Skirmish games.

I know what he wants but that doesn't work so the best thing would be to name a hc so that the host should put fast as game speed.