Hi,
On the one hand, I think this possibility to set overbooking on the resource level is very good.
On the other hand, I noticed that project managers also like to see an ideal state, how the project would go if the assigned people would only work on that specific project. (Don't ask me why.) If you would like to achieve this at the moment, you have to set overbooking one by one for each resource, and it may be inconvenient.
I have an evolution idea, and for that, I created a first version based on v8.4.4 :
I slightly changed the planning part to have a checkbox to calculate planning with "infinite capacity of a resource". If it is checked, then capacity is calculated almost as if for each resource 999 FTE was set for overbooking. (It behaves only almost as if we were setting overbooking one by one for each resource because currently if I set allocation of a resource for a project to e.g. 60% and I also set overbooking, then 60% is not taken into account anymore for a given project. In my version, 60% is taken into account for a given project on a weekly basis. For me, this latter seems to be more reasonable than how projeqtor works at the moment. Although, I don't know if my version calculates correctly in every case.)
I attached the files and two screenshots. It might be useful to add that kind of feature to the product.