Both
Engine designs, GE and RR, have "bypass" for Fuel. It is at the FMU in the Trent, and the HMU in the GE. In this case, Fuel in excess of combustion requirements, (Spill) returns to the HP via dedicated plumbing.
I would agree "weight" isn't an issue for an additional bypass for Fuel around a clogged or malfunctioning FOHE (F/O HX in GE). I also don't think complexity is an issue; GE has some complexity that Trent does not.
The GE design has three separate Heat exchangers, Trent only one.
Two of the GE's units are included specifically to mitigate Fuel icing.
The Main HX and the Servo HX are paired in the Low Side, and the schematic states they "Prevent Fuel Icing". An additional HX uses separate sourced Fuel to cool the Gearbox Oil.
Here I need to back track and perhaps apologize. On different occasions I have read here that GE's HX is downstream of the HP Fuel. I now believe that not to be the case. It remains a question; the schematic I use is a simple one, the orientation of the Main F/O HX cannot be perceived conclusively. In bsieker's post #2316 he demonstrates his idea of the critical architecture, HP in front of HX. This I think if not wrong, is not accurate to certainty.
To be quite fair, though the schematics I study are from a common source, again they are not blue-line exactly, and I regret any mistaken conclusions I may have encouraged by being so convinced of conclusions by others and myself.
This leaves a major discrepancy. GE in its schematic clearly has addressed Fuel Icing (potential) in the text of their document. Rolls has not. This does not mean Trent didn't consider Ice in Fuel, just that they didn't mention it in their schematic's text. Include a reasonable vulnerability in the architecture relying on one FOHE, without Heat, (Other than Oil), or Flow Bypass.
NTSB's release and letter continue to shadow the 200-ER. I still don't see the proposed mod to the FOHE as a "Fix". There may be other steps in Rolls plan, but without knowing what they are, the change doesn't address the known Icing other than to try and keep it melted. A very abbreviated Fuel testing program brings up new worries; it didn't solve anything, and really hasn't even identified the specific problem or its potentials.
AF