Yeah, I'm not sure a full rebuild is doable within a single season. I mean it's going to take all that time just to expand the existing one.
I think the idea is that this is the quickest way we can significantly improve capacity and get a nice chunk of additional revenue in. The 6k increase is enough to get us £10-13m more matchday revenue per season, but not so large that we have to find a huge number of new matchday regulars to fill it.
The big test will be what happens next...