Honestly sabse pehle kuch Shatabdis ko Vande Bharat rake se replace karna zyada better hoga.
My preference for Shatabdis with VB rakes -
1st should be Bhopal Shatabdi under any circumstance. The return arrival time needs to be sorted out at NDLS and a VB rake can help a lot.
2. MAS-MYS Shatabdi.
3....
more... MMCT-GNC Shatabdi
4. NDLS-LKO Swarna Shatabdi, which can be extended upto Ayodhya in future. (Might be a bit controversial, but the opinion my opinion for extension is only because Tejas on reverse timings is already there)
5. NDLS-ASR Shatabdi (12013/14)
6. NDLS-AII Shatabdi.
This is only my opinion though, as IR does not seem to have any plans to replace Shatabdis with VB.