I thought that there weren't enough 390s to cover all the existing diagrams, which is why the Scotland via Birmingham is sometimes run by Voyagers?
Yes indeed.
There are only a few options for VT to run 390s to Blackpool.
There are 4 early starters from the Preston area:
0513 Lancaster-Euston (390)
(0539 Blackpool)-0600 Preston-Crewe-Euston (221, merges with Holyhead portion at Crewe)
0617 Preston-Birmingham (221, an early part of the Scotland-Bham-Euston service)
0658 Lancaster-Euston (390)
You could start any of these at Blackpool.
But the rest of the day these trains all go to/from Scotland.
So its not easy to see how extra services can be provided without new stock, which won't be forthcoming until 2020, possibly only when HS2 comes on stream.
Running anything via Bolton deprives Wigan/Warrington.
I should think there is still a possibility that VT will just keep the timetable as is.
You are not going to fill a 390 at 6am at Blackpool.
(Off topic, sorry, should be in the Blackpool electrification thread really).