While I initially intended to use this with the 25/28mmGrenadier range of figures, it will work well enough with the newer, slightly larger 30mm ones as well. Short of converting your own incorporating bits of the toy castle, this is your best option.
A scale shot with the Quest Miniatures He-Man, showing the separate Point Dread and the configuration where it's mounted on the castle. As can be seen, the towers are the weakest point regarding figure placement as the tops are quite shallow. The Talon Fighter is in itself a useful addition as it works well enough with the scale of the figures.
He-Man doing some more posing on the rooftop. There is enough room there to place some figures:
The other sides of the model:
He-Man waving you off (or kicking you out...):