There is no max at least any reasonable one in Lower Tier. Total limit for arena size is somewhere 22k.
I have understood that Bleachers are most related to current success and Luxury Boxes are related to your fan club size (season ticket holders). So you cannot convert your Bleachers to Luxury Boxes. You can set Lower Tier very big and price very low, then you would get more Lower Tier spectators. However there is no proof that your total income would be remarkably higher.
Try to keep you arena balanced....
I have always tried to maximize income per seat category. I mean that I always calculate how much money I have got e.g. from Luxury Boxes, then I build some more and then I try to set ticket price so that I got just a little more than earlier if that seat category would be full.
In the end (after several seasons) you will have 50 Luxury Boxes, 500 Courtside, about 3000-5000 Lower Tier and rest will be Bleachers (15000-17000).