Thanks for the update.
In my view, the below extension is feasible and entire TVR/NGT section gets connected with TPJ @ night time too.
1. Extend "76820/Tiruchchirapalli - Thanjavur DEMU" to TVR/VLNK with below timings
TPJ - 20:30
TJ...
more... - 21:55 22:00
TVR - 23:00
NGT - 23:30
VLNK - 00:00
This DEMU has connection/link with TVC-TPJ intercity @ TPJ, so it should give good no. of pass to TVR/VLNK.
2. In Return, it would starts at as below
VLNK - 03:30
NGT - 04:00
TVR - 04:30
TJ - 5:40 (As such 76823/Thanjavur - Trichy DEMU starts this time)
TPJ - 6:45 (As per TT it reaches 7:05, post doubling it would reach 6:45, then only it would benefit to catch TPJ-TVC intercity @TPJ )
3. Also extend "76820/Tiruchchirapalli - Thanjavur DEMU" to TVR with below timing
TPJ - 1:10
TJ - 2:30
TVR - 3:30
In return,
TVR - 05:30
TJ - 06:40
TPJ - 08:10