Thanks for putting this up!
I can see the advantages of having a second bridge available, also for security reasons. I like also your mention with the Transmuter pool type (Upload Transmuter Contract - #4 by LeonoorsCryptoman), because that will greatly enhance the UX for bridged assets which might have different affixes. I can indeed imagine that the user bridges an asset; shows just the asset on the Osmosis front-end; and where the backend takes care of the necessary swaps to give the user the best swap-rates.
Good that you also give a mention already how we should cope with assets which are already bridged by our current canonical BSP Axelar.
How do you see the part where the affix has to change for the leading bridged asset? Are you not worrying that it might be a bad UX for the people who already bridged the asset in the past from the leading bridge provider at that time? They might be confused that they now have another asset than they had in their wallets. I personally would like to hold that part of the proposal until we are more clear on what the Transmuter contracts can do for us. The problem might solve itself that way already.