I would suggest that you still need in-game money to initiate the construction of the seats, but then you can pay to have it completed right away (or pay half that amount after half the construction time to finish it).
I agree with you that it should be prevented that the game ends up as pay to win, but it seems we differ in our view on what is pay to win. I'm someone who doesn't want to pay for feature, advantages or speeding up things, so I'm on the same page as you in that regard. However, I do try to look through the eyes of the paying users and of BB in the sense that the things you can pay for need to be attractive for those that pay for it, so that BB can generate money. If micro-transactions are limited purely to cosmetic features, I think it won't generate a lot of money because there's not a lot of people that want to spend money on that.
However, I think the newer generations have a need for instant gratification and are willing to pay to get things faster. That would generate a lot of money for BB, and more serious projects like an app could be developed with that. That's a positive for non-paying users too.
In the end, if you want a good game, it needs to be paid for. I'm perfectly fine with paying time for a game while others pay money. That way I can profit from the money they invest in the game I play for free, and I'm fine with having to spend more time to get to the point that paying users get faster.
As an exisiting manager, I'm not negatively effected because I already have my arena and good roster. As a new manager, you could experience a negative effect. You could combat that by also paying to speed up progress (new generation might do this), or you could just go for the long haul (older generation like existing managers might do this). However, since new manager already face the disadvantage versus exisiting managers, I don't think giving the option to pay for progress is detrimental to the experience of new non-paying users.