Surely this isn't going to be the Hugh Lane all over again?! Please in the name of all that's sane do not let this be another "oh but it's only glass, it doesn't actually exist" infill extension.
Sounds like that's exactly what will happen.
I think it's a wonderful idea to use it as a public building, but I don't see how it could be large enough for a new central library unless there is a large extension. Maybe if it's around the back it won't be too bad?
The ILAC library is truely abominable.