I played a bit at centre about 30 years ago, maybe I should have a go?
Just shows that going into the season with only two bona-fide centres has blown up in our faces. IMO Blackmore isn't so good with his lateral movement and could easily get caught out in the centres. It's a really difficult position to play defensively as every decision is a potential try saver.
Picking Myers would be a real baptism of fire for a kid. I'm still hopeful that Gill makes it, even if he's only 70% fit.
If there's no Gill I'd probably go with Myers but have Blackmore, Tindall or DFJ outside him. Preferably whoever is the best communicator who can nurse him through positionally. I'd also not have Appo inside him for that reason - Myers will need an experienced backrower who's a good talker on his right to help with the inevitable traffic that would come his way.