That would be interesting! We'd be like a clown car. Two adults and three teenage boys! LOL Haven't booked yet. Was just wondering what they "typically" offer. I've heard that there aren't tons of compacts at MCO. Wonder if that's true?
Economy and Compact are actually the most popular sizes. They are so popular that they will quite often be sold out and the rental agency will first try to sell you an "upgrade" to something larger. If you decline the "upgrade" the larger vehicle is usually just given at no extra charge (since the smaller car is sold out)
If you watch prices on rental cars for awhile, you will often see mid-size or full-size actually renting for the same or less than Economy/Compact. This is because the demand for the small fuel efficient vehicle is high and expected to sell out (price goes up), whereas a FS or SUV may have lower demand and may not be looking to sell out (price goes down)
This is the reasoning behind the "Lock Low and Go" category with Dollar/Thrifty. You are basically renting at the Compact price and the rental company has the option to give you just about any vehicle that they have too many of at the time. This may be the Compact that you are paying for, or pretty much anything else they have in stock that isn't in demand at that time (Mid-size, FullSize, Standard, Premium, SUV, Minivan etc)
Hertz has a category called "Managers Special" that works the same way.
Alamo and National allow you to pick whichever car you want from the aisle size that you book. Nationals Emerald aisle can have just about anything on it, join their Emerald Club (free to join), book a midsize and pick anything from the Emerald aisle. Alamo's Full Size aisle will have FS, Premium, SUV, Minivan and sometimes Luxury or Sport models just depends what they have lots of that isn't renting. Each aisle has it's own size vehicles and often has larger size vehicles included (ie: Standard in Mid-Size aisle)