> light losing energy to radiation as it travels

> I've not found anything to fully discredit it

Well, for starters, there's the minor problem of light never having actually been observed to lose energy as it travels. If light loses energy to radiation as it travels, then this radiation should be detectable. Where is it?

Then there's the slightly less minor problem of having to rewrite all the known laws of physics from scratch, starting with electromagnetism and quantum mechanics. (I presume that you're not going to toss out conservation of energy because the whole point of the exercise it to account for the cosmological red shift, yes?)

But other than that, I can't think of anything that would discredit it either.