I agree about making it browser based. Keep it easy so anyone can quickly access the cameras, without downloading or setting things up.
Is the idea to have a PTZ in a central area and then have presets for each unit? That could be useful.
Are all the cameras outdoors then or?
This is a 200 unit 3 level construction site. The PTZ cameras would be located outdoors at a central location - likely pole mounted. One PTZ could be used at the start of the project but due to the layout the Developer will need a 2nd PTZ to properly cover. The second PTZ would be on a 2nd pole.
USrelay may have what you are looking for with the ability to manage users, limit time on website or camera.
Here's a website designed for marketing purposes that my web developer put together for a construction customer using a fixed Mobotix camera.
I have a webapp that does something similar to what you want.
IMO, don't give users direct PTZ access, you'll end up with too much contention and other issues.
What I do is have a PTZ that is programmed with presets. Once an hour I grab an image from each preset point and catalog them on a site that makes it easy to review. You could even assign user logins to each preset point. Users can then see current status, progress over time, etc.
For the most part I don't think it's a huge marketing tool for people to be able to watch the general construction live, but I do think people would enjoy seeing basic progress.