building high in trees is indeed difficult. i learnt it the hard way, but it is still something doable.
The hardest part is that the surface you can work with depends on the size of the tree branches (the very big ones of course) and the size of the tree trunk. Of course you could get a lot more surface by using a lot of pillars making the jonction between your house / base’s foundations and the ground itself, but it would ruin your design and i’m sure you don’t want that.
So, that said you should keep in mind you cannot plan on building a large house if there is no HUGE hanging branch or if you’re not using a lot of pilars.
Everything around the tree trunk is buildable as long as it does not exceed sthing around 2-3 foundations width, so it’s still very limited imo but you could come up with a special idea all around this trunk.
in short don’t be too greedy with the size of your structure, you’d better try to build several little houses than a single big one.
best is still to try things out by yourself imo, but if you can come up with more precise questions on your topic, me and others may be be able to help.
hope it was understandable.
good luck !