Is it possible to code the 1x1 heliport as either a 2x1 or 2x2? I've been playing with it off-and-on all night using the airships from Generic Av8 and I can't seem to find a nice spot to align it with the nose of the ship, crowded up against the east edge of the tile. It seems to look best near the southeast corner but would need to overlap the corner to do so.
You could write an airport newgrf which replaces the heliport. The movement pattern will stay the same (including landing height), but you can adjust the looks of the tiles as you like. Not sure, but it might turn out difficult to attach tiles north of the landing spot as the fsm stays the same.