I remember seeing that thread, but didn't realize it included buses between MK-TTC. That is a good thing but, if they don't plan to run regular buses between MK-TTC, as suggested in the
WDW magic news article, then when there is an issue with the monorail/ferry they would still need to find buses and drivers somewhere and send them to MK. This is why I think it would be the most difficult of the three. Extra buses are easy to keep on hand, extra drivers, not so much.
You could definitely reroute buses from other resorts/parks, but they didn't do it in this case or the other one that I read about from early June when the monorail broke down. In this case I can understand why they couldn't reroute buses, but it still raises the same issues, if you aren't running them full time you don't have the drivers to staff the extra buses sitting around.
Hopefully the new capacity buses will help, still wouldn't mind seeing another ferry ($$$) as well though, and a walking bridge to GF.
To be fair I am not a transportation engineer so I am just going based on my observations.