If Daeron wasn’t killed by treachery but rather say a stray arrow in battle or, since he probably led from the front, battle wounds either during or after a fight, how would that change things?

It would change his legend a little – glorious death in battle vs. cut down dishonorably. It would, however, change Bloodraven’s reputation quite a lot: while there’s too much stacked against him for him to have a good reputation, he wouldn’t be singled out as a kinslayer until much later.