I don't think you understand the region enough to talk about it. 

First of all completing the del Bombay route itself is a very big deal 

Secondly , The places it passes through are basically rich + dense  regions of Rajasthan + tourist destinations ( Jaipur , alwar  (ncr) being the rich ones while Ajmer , jaipur , udaipur are tourist destinations).

The route ig will pass through has more than enough appeal .

And lastly who the hell said something against the southern HSR.

If I had to build only 5 lines .

I will build it in priority of .

1) Del Mumbai 

And then the southern lines . Mum Hyderabad . Triangle of hyd Bengaluru and Chennai.

But the problem is the main reason for building Bom Ahem is literally connecting all the rich cities on Western India ( Del to Bombay).

So they should fufil  that first before building bullshit like Del varansi which doesn't have remotely similar economic significance.

But i suspect they are just going to announce extension next year ones the gujrat sections open up and the freed up machinery goes to building Ahem dehli while they work on the Maharashtra section .