If you could set other macros through this command it would be possible. Just make three macros that set the subsequent one to the same slot on the cross hotbar and BAM you just saved 2 slots.

Of course this would probably be stupid without another added function like "On Hit" or whatever that will only execute the /crosshotbar command when the ability from the previous line scores a hit. Otherwise you'd be wasting two actions not being able to go back to Fast Blade if it missed the first time...

I guess maybe it's too much to ask for expanded macro capabilities like this but it would be really sweet to be able to do stuff like this. Really just adding a 'macro' subcommand to the /crosshotbar command would go a LONG way since you could setup macro cycles on a single slot.