Mads, it would appear that if SGP can wait for a certain time to start a sequence, it could equally take the target RA/DEC coordinates and local time to calculate current target altitude compare against a starting altitude. I think it is already on the feature request list. Thinking about it, the pre-event scripting feature currently in SGP might accomplish the same thing - start the sequence but hold the event until a VBScript said the mount altitude was higher than a threshold.
For info I did some more googling on ACP planner - and came across this free editing utility
http://astronomy.mdodd.com/planalyzer.html