remake

You could simply create two campaigns.

That makes sense :) But let us finish at least one... I'm afraid of messing up the last one - it's terribly tedious to create a beautiful map larger than average.

Since the campaign is based on WoG, its features should be taken into account. A hero who carries over from mission to mission also carries over the commander, which makes the start much easier. Therefore, the start should be made more difficult.
I also don't really like the abundance of empty space, especially in the first mission.

I don't HAVE commanders! I have WoG 3.5! There's just nothing to fill that empty space with. I can't just plant a forest. Besides, there's a type of terrain in nature called "steppes" or "meadows." Consider it to be that ;) I don't see any more empty spaces.