Like you, I am not too concerned about warranty work by the time the 24K has expired (which for me will come well before the 24 months). Most repair work will be then of the routine, periodic type, and I think that two years or less down the road there will be information and dealer parts available so any independant can do that sort of thing. There will be some few instances when smart maintenance may be more appropriate. But my plan is to continue my AAA coverage on both my vehicles at the Premium level wherein I can get one 200 mile tow and four 100 mile tows to the repair station of my choice each yearly renewal period (if the car is disabled and has to go to an actual smart dealer). My reality is that I can travel anywhere along the Eastern Seaboard and inland to the Appalachians from the Outer Banks, NC to Portland, ME and be within 100 miles of a smart center.
Separately I have suggested to smartUSA (HQ, not IB) that they offer the sale of extensions to smart 1 service after the warranty expires. The suggestion was taken favorably by Ken Kettenbiel though I haven't heard any more from them about it.