Okay, fake!Daeron would be such a banger ASOIAF POV character though:
Being the son of a lowly merchant family and getting coerced into this whole hare-brained scheme on threat of your mother being hanged
Getting the comforts of a noble soldier on campaign but knowing full well your life is deliberately expendable
Spending some time with actual!Daeron to learn his mannerisms, getting to see how he feels about the swap plus the whole civil war situation, and then maybe some kissing on the side coz knights of summer and all that jazz
Having to occasionally hang out with canonically beautiful yet dangerous and not-actually-bonded-to-you Tessarion to sell the lie in public (maybe with actual!Daeron being concerned yet helpless nearby)
And then getting whisked from all that on dragonback by Daemon the Rogue Prince to meet Queen Rhaenyra and live as a hostage behind enemy lines
Like, honestly the reason there isn't a fake!Daeron in the book is coz George would have dropped the whole book and written a fake!Daeron novella or something!