I am trying to clarify exactly what you are trying to do, it is true that the current functionality is a result of the SL functionality plus innovations by the OS devs, so as Bo mentioned, any further innovations will be done by these devs, if you have abilities in coding maybe you could join the dev team and bring about the required innovations, because every innovation needs to be thought up (which you may believe you have done) introduced, tested and included in core, and the dev team probably already have a list of priorities that they are currently working on.
In the meantime we find workarounds for functions that are lacking.
You have a building with 500 objects and you want to be able to package this for distribution??
You mentioned yourself that this is possible via a builder script, the fact that each item must be taken into inventory and then moved to base object is just part of the process,
This is not possible via scripting, for reasons only known to LindenLabs, and obviously not known to anybody on this site. But there is a reason.
and yet it is possible, you just said it is, its just a lot of work, but I dont see how you can say its not possible.
So what happens when I change a few objects in my building, or move a few objects around?
why cant you just replace the few objects that have been changed into the base object? each item has its own positioning (component) script, so long as it has the right name (the name that it was originally saved as) then maybe it will still work (I've not tried it, but it would be my first port of call) I wouldnt think you need to redo the entire 500 items.
llGiveInventory() is not appropriate. This function allows me to take an object from my prim inventory and send it elsewhere, but does not allow me to take the object itself (which is what I want).
could you give an example of what you want to do please, I am not sure I understand your needs, because to me llGiveInventory enables an object to give its contents to you, is this not what you want?
why is it not possible to tell and avatar to sit from a script?
again please forgive me for not understanding your needs here, "tell an avatar to sit" seems like you need a chat bot to say "sit here!" so I must be missing something, maybe we can find a workaround if we can clarify your needs