In my opinion, All long distance trains, which are prone to get late and has less TAT comparatively must have RSA pattern like Mahaabodhi and GAYA-MAS SF Express. The idle rake 1 train may act as spare rake of another daily train if that late running train is running quite late and is on verge of getting cancelled.
For example:
1) Rake of Marusagar Express can act as spare rake for AII SDAH on Wed and Thursdays.
2)...
more... Rake of Ziayrat and NTSK RJPB together can serve as spare rake for Sampoorna Kranti, if 13281 comes ontime, and 12394 arrives RJPB 12+ hours late on Tuesdays.
3) If 12273/4 Duronto is LHBfied, it can act as spare rake for Poorva on Thursdays from HWH.
4) Rake of YPR-MFP Express can act as spare rake for Sapt Kranti Express on Saturdays and Sundays, if 12557/8 is running quite late.
Please Note: Zones must do a few CC changes, but I think that effort is worth and better than running train very late or cancelling them.