Also more a question to locals: How bad is the current system actually? From my limited experience the current system is not perfect, but does its job. Let's also not forget that the current system is more flexible in terms of future expansion. Busses are relatively easy to add to a new hotel, a subway system is less flexible.
I'd argue the system (if you can even call it that), barely works. Currently, it's comprised of public Lynx buses, privately chartered buses, rental cars and Taxis/Ubers.
There's essentially two very different people to tackle when it comes to Orlando's transportation: locals & tourists.
The tourist solution is relatively simple in my opinion. There's essentially 4 major "pockets" in Orlando that tourists tend to gravitates towards: North I-Drive (includes Universal), Vineland Outlets (lots of hotels in the area), WDW, and US 192 (outside of WDW). All we really need is a connector to and from the airport, a major hub, to these smaller hubs, and we can then provide a localized transportation system that connects everything within that smaller hub (mainly hotels and restaurants) and the major Orlando destinations - the parks. The I-Drive solution is easy as everything is up and down one long corridor. Hotels not directly on the street, are a mere 5-10 minute walk away.
The major issue to address is that the connection between Tampa and Orlando has reached it's capacity. Orlando, as a region, has grown beyond WDW and into the western areas of Orange County and Lake County (with only I4 and the Turnpike going completely around the large WDW property as it's only major connections). The counties and developers didn't care to think things through... so it's led to congestion and there's not much we can do there as you can't stick a highway through WDW property (they've planned on a Epcot Center Dr expansion all the way through to 429 that would help alleviate major congestion). Currently, we're receiving an expanded highway (as if that'll work) and
eventually, the Brightline connector over to Tampa that may take a few cars off the road (it won't feel like that though as Florida's population boom will easily offset this).
I'd prioritize getting tourists off the streets first as that should be a quick and easy solution that most people (except Mears) would agree on.