I'm not against the city investing to turn it into a permanent stadium but converting common lands to private-only use does give me pause.
In other words, my impression of common lands is that they should be available for anybody to use. If they are converted into a stadium to be used by a profit-based private entity requiring the public to pay to enter, it seems a line is being crossed that goes against the concept of them being 'commons'.
My opinion would lighten if other not-for-profit entities, such as schools or other amateur leagues, were allowed to use the facilities for their games, which would provide more public benefit, IMHO.
Non-pragmatic reasons, such as pissing off "friends of" organizations seem a little silly, though I appreciate the humour.
I would like to see the space elevated to a higher use level than it was previously, but I would also like it to be considered carefully when public land and tax money are being used for the purpose. For example, I'm curious as to the investment ratio between the football club and the city for expenses that specifically benefit the professional-league uses. It's not uncommon in a lease situation for the lessee to pay for modifications of the property being leased that benefit the lessee in the use of such property, and I would expect this to be the case here.
Also, I would like to see more data on attendance longer-term, to fret out whether current attendance rates are simply a reaction to "freedom" from pandemic restrictions easing up (and perhaps some fans will eventually find other things to do with their time) or if popularity of attending these games continues (or increases). If the demand continues, then it would be a stronger case to green-light a permanent stadium with higher capacity, in my opinion.
As far as relocating the stables, I don't agree with this, as it has become a longstanding tradition for the area, and IMHO many people enjoy seeing the horses there, even if they don't personally use the facilities. Interest and demand still appears to be strong, even after all these years.