No, it is not win win situation for all. In Delhi around 15 - 20 Uttarakhandi population reside who make frequent trips in this route. Apart from that tourists from around the country take this train form delhi which has convenient overnight timings for the change of train at New Delhi. It is these people who fill this 11 coacher AC train at least one week advance round the year.
Now, for 12206 there is no issue, ddn departure will be in GN quota as its now, but 12205 passengers at ndls , will they be in GN quota , it will be in remote or pooled quota, I guess.
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alternate arrangement will be there for this crowd. new Delhi being national capital is having dedicated overnight for almost all routes. why severe them of this most demanded route. Provide new train for them as Mussoorie exp is of no use in its current slackful timings.
Also can kota students fill 11 ac coaches round the year, if not then these seats will come vacant till delhi. For kota students normal sf overnight train having sl and gen coaches and departing kota after 10 wil be more suitable , which will reach delhi early morning. And there are multiple ways of rake utilization. By making a pool of 4 rakes ( like that of dbrg/rnc/bp/jat rajdhani at ndls ), they can run new day time trains to other parts.As from delhi all northern parts of country overnight train runs whose rake lies idle in daytime at various delhi stations.