from memory - so I apologise in advance for any errors, and with the caveat that I'm a pretty new player with little experience....I've had a go at fixing this sort of thing myself, and it went something like:-
Load the mission in the mission editor, then click on your helo to select it....if you aren't sure which icon is your helo click on the small icon for show all units (or something liek that) 2 above the bit that says 'map' on the left side of the screen, near the bottom left corner. You can look at the unit info on the upper right of the screen to confirm it's your helo, in the 'skill' box it'll say 'player'.
Select the waypoints for the unit (lower part of that right hand column of info, it's the leftmost icon of about 4 or 5) you can select the first waypoint (ie the start position) and there's a dropdown to select from - three of the options are to start from the ramp, runway, or a parking lot - if you click one of these it'll jump the waypoint to a nearby (nearest?) airfield or whatever to let you fly from.
You might have to fiddle a bit, and it can backfire a bit in that on one mission it jumped the waypoint about 50 miles to friendly territory (no surprise I guess).
There may be better ways to do this, but I had the same thought you did and this is all I've found so far to get it done. I'll be playing with the editor some more, maybe get back with a better version some day! (I'm also setting up TrackIR and Vocie Attack for the Huey, so I've a lot on....)
Dave