ИДЕЯ ДЛЯ РИЗОМА

Raise the library limit for R2.

Try building a forest in one of the forest land scenarios that is even near as dense as some parts of the in-game forest...and then try to add animals and/or homin, not to mention whatever you were thinking of actually doing in the scenario. Then...try to add another Act or two. I was really excited when they released R2 and I have spent a lot of time building scenarios, but I have built very few which lived up to what I was attempting to build for this very reason.

Or, maybe implement a scoring system, let us work to be more "trusted users" and get bonuses to our limits.

Quite. All scenarios I've built have been desert, lakelands or small for this reason. There's no way to build a large forest and still have anything in it (since a moderate camp is already easily 50 scenery objects).

The entity limit is fine imho, the scenery limit could use a push or a change. Right now you get a global scenery limit for all maps your scenario contains. This makes no sense as only one map is loaded at any given time. So a limit of 200 scenery for 5 maps reduces it to an average of 40(!) scenery per map.
Change it to 200 for each map or increase the overal limit.