The Transfers only make sense if they go downward and I will tell you why.
(if) you made transfers up there is always a chance that the server(s) that you transferred off from would be diminished greatly in population where you would need to again transfer to another classic server or do server merging (more work for blizzard to do)
Where as if you do the transfers downward you can funnel together all the players whom want to stay playing on classic eternal and there would not ever need to be any issues with low pop servers due to a lot of people progressing. Ensures strong populations grouped together. Better to have 5 high population servers than 40 low population servers.
With that being said the smart choice and the logical choice is the transfers downward. Best option to ensure classic only eternal players can play with other classic only eternal players on a classic eternal server.
This is why this is the logical choice