As mentioned earlier, on the "path" between the Grand Floridian and MK, there is a much-used "inlet" of water which is where the "Electrical Water Pageant" barges are stored. That would require a new bridge to be constructed and that bridge would either have to be an expensive "drawbridge" (I know they CAN do that, there's one on the WS Lagoon in Epcot, near China and "Africa") to allow the use by the EWP barges and possibly other higher profile watercraft, or simply find another waterway area to store those barges, etc.
But that side of the "loop's" problems pale by comparison to the MK-to-TTC section of the walkway.
It would require a wide, safe foot-traffic lane that runs through the same "under-the-water bridge underpass" portal near the front of Contemporary.
Back before MGM and several new resorts were built far removed from the monorail lines (and necessitating the operation of MANY new bus routes), save for those guests who drove to the CR, this ugly, narrow passage, with its steeply-inclined approaches and many exposed pipes and conduits, was never seen by most guests... UNTIL WDW decided (wisely) to put the resort bus stops for MK over AT the MK front gates (and not at TTC).
After that decision, the idea of threading a guest walkway though this too-small and now VERY BUSY underpass was simply not feasible.
