I can see why it's hard to imagine Bloom trading any highly regarded prospect or young player, and similar things were said about Ben, before DD took over. I'm not so sure we can assume it is a rock solid tenant of Bloom's philosophy on roster building or has just been a strategy put in place to get us to a point, where the priorities can change and so do the strategies to meet the new circumstances.
I have no basis for this belief, but I think Bloom will eventually be open to making a big trade, or he may be steered into doing one from above, but the timing of such a trade would likely only happen when the organization believes at least two things are in place, and I'm not sure now is that time:
1. We have a major league roster foundation set where only 1-2 major additions are needed to open a highly competitive window of at least 2-3 years.
2. We have a farm system set up that can afford to part with a package big enough to land a top player but still remain strong enough to promise continued infusions of talent to the big club.
I'm not sure we can ever get to this point, but personally, I think we are close, now. A third aspect to the 2 major points above might be that the budget is set up where there is very little deadwood, and going over the tax line is possible due to the previous season being under the tax line. (This looks okay, now.)
To get a major young pitcher, I have to think it would take Casas or Mayer. Trading Bello defeats the purpose of improving the rotation. Anthony's stock is on the rise, so maybe he could be a centerpiece. I would not be for trading 2 of the 3, and that might be what a team would demand, but I'd say no to that.
We aren't getting a top pitcher by trading 5 second tier prospects or young players from this list: Duran, Bleis, Houck, Yorke, Rafaela, Crawford, Perales or Wikelman.
Here are the values given by BTV:
59 Mayer
47 Casas
41 Anthony
40 Devers
39 Bello
29 Bleis
27 Houck
25 Duran
19 Yorker (perhaps over-valued)
17 Crawford
13 Yoshida (likely over-valued)
10 Verdugo
7 Screiber
6 Rafaela (likely underrated)
6 Wink
5 Drohan
4 Perales, Wikelman, Wong & Romero
3 Meidroth, Walter, E R-C, Abreu, Urias & Alcantara
2 Pivetta, Cespedes, Bastardo, Monegro, Mata, Murphy, Castro, Hickey, Brannon & Bonaci