If we had good offers for Branthwaite, Onana & Pickford and only needed to sell one--to reinvest...the obvious one would be Pickford.
Both Branthwaite & Onana have over a decade in them while Pickford only around 5 years. Meaning its expected two values to increase while Pickfords will decrease due to his age.
There is a risk where we hold onto Onana & Branthwaite and injury may occur. So its very difficult when to know to take the money.
What we know is that we have to "build from the ashes" as you wrote.
For me, its one of three options:
1: We move on a high number of lower quality players while replacing with a small amount of u21s of a high potential and with lower league experience e.g two players for the right linked: RB/RCB Van De Ven (Boro), RW Asprilla (Watford).
-- Dyche rarely uses subs and so a small squad of e.g 18 + youth players could be fine for next season. Low incomings with high outgoings.
2: Similar to (1) but also sell one of Pickford, Branthwaite or Onana.
For me of the three, id sell Pickford as his value will be at its peak. I would have done this last summer and brought in Verbruggen (now Brighton) or Mamardashvili (still at Valencia).
This summer id be looking at the likes of Mamardashvili or Trafford (Burnley). This should be seen as bringing in a young player of a high level who can also become superior to Pickford. While also generating enough funds for another outfield signing.
-- Im sure we would all love to keep Pickford but as weve seen at RB with Coleman, holding onto players for too long sees their value plummet + can leave us short in quality in comparison to the ageing player.
3: Full on carpet bombing of the squad selling all three of Pickford, Branthwaite, Onana and bring in a new GK, CB, DM/CM, ACM, CF. A new spine and also several new players for other positions as well (e.g new right side).
A massive gamble but on the other hand the team and squad may benefit from a major refresh. It may give the team a new identity and under Dyche for a season before the new stadium it could be the perfect time and perfect manager with low risk tactics.
Thelwell has some major decisions to make.