Maintenance for trains during normal hours?

I was talking to my wife recently about the NEL breakdown when she made a comment on why maintenance of the trains cannot be done during normal hours if they do not have time in the early mornings. That set me thinking about the possibilities of that happening. In fact, I think it is possible.

The concept is very simple. The MRT operators will have to maintain buses to backup the train operations in the event that the trains breakdown for long periods of time. Why not use the buses for other purposes? Why don't we just shut the train operations down for extended maintenance, and let the buses ply the routes for all the train stations if extended maintenance hours are required?

The train operators will get the extended maintenance window needed and the "backup buses" are deployed during this period. The problem will be further reduced if the bus operators are allowed to duplicate the train routes so that we have alternate ways of getting to our destination.

I guess this will also push the train operators to better maintain their trains and to excite innovation instead of spending the time opening more shops in MRT stations.