Why not simply create another CP?
I did that with success in a similar case - model with theodolite GCPc.
When I took additional fotos of a site, one marker has been almost entirely washed off, only one corner was still identifiable.
So I went back to the older model, created another CP at this corner, took the coordinates and created re-created it in the new model. Writing this I realize it would have been even easier to simply export and import the point… 
Not quite as quick as your request but not too much effort either.