chris
I have no naive trust, at least not relative to that which I had years ago.
I think a 'simple bypass system', may have been looked at prior to original design vis a vis Trent8, but frankly, I think it is being actively avoided at this point. Retro isn't simple, it isn't cheap, and it isn't logistically benign to any of the principals.
As read, the AD focuses solely on the FOHE. airfoil was the first to point out its design purpose did not include Fuel heating. If it did, Oil would not bypass its chamber as a designed mechanism (oil bypasses now only when it itself does not need cooling). This also raises questions about your faith in an a priori engineered look-see at the potential for Fuel Ice.
Since there is no provision for Fuel supply to the powerplants if for any reason the FOHE is clogged, one doubts the thoroughness of the investigation for potential Fuel starvation due to such a problem.
One could make the compelling claim that in the absence of an alternate path for fuel bypassing the FOHE, the sacrifice of FLOW (fuel) was not deemed to present a critical path, ipso facto; there was a determination made to exclude such a safety implementation. To think that it was excluded by accident, is beyond even my cynical approach and suggests our shared faith in the engineering, though from different perspectives.
Will