Burnsland - welcome to the boards!
The area behind Fantasyland was prepared so far as cleared and foundations prepared for parking and vehicles access, drainage etc. Anything major this side of the railroad would need foundations anyway like a regular building (as opposed to whats needed behind the railroad)
As you said though, this is a major service area, if not THE major area. Apart from parking and CM access, many utilities are found here, backstage access to HM and IASW, plus its the main entrance to the Utilidors - which in itself would be a BIG job to extend. Not to mention utilidor access is needed 24/7 for deliveries, service, CMs, Payroll, plus I imagine medical emmergencies etc. The whole arc of the 20k lagoon, show building and drydock, Toontown and the Raceway could easily hold another land and/or another Toontown, or 2 E rides and Toontown, or a D and E Ride, or...... lots of possibilities.