I see your point and have even thought of suggesting it myself, but I started thinking of the details in how it should be implemented;
- What happens if you have more than one fleet that a stack potentially can board?
- What happens if you want to embark/disambark part of the land unit stack, rather than all at once?
As it is now, it works just like any other situation where you merge/split stacks, which in my opinion works just as well, once you get used to it
As for Island 10, if you are thinking of marching there, it's in the middle of a swamp (IIRC), which makes for a strenuous march even in nice weather.
