Sorry but this all seems mental to me. EJ clearly doesn't see Mercer as an international 8, and frankly neither do I with Dombrandt, Simmonds, Earl, Wilson, Curry and the young Willis all playing better or similar rugby. As a result, EJ's made it clear that Mercer isn't part of his plans and so Mercer is rightly taking a bigger contract in France rather than getting paid less than he's worth in England in the hope that he might get another opportunity. Surely by not stringing Mercer along and making it clear that he's better off taking the contract, EJ's doing the right thing? It's a shame for Bath that Mercer's left but it's not EJ's job to keep players in Bath; it's to pick England squads, and he (IMO, rightly) doesn't see Mercer as a part of those squads.
It's also no good bringing up a load of players who might leave as a result of not being picked as none of them have left, so presumably they're still in contact with EJ.