Even if the Embraer (or even the A318) had the range out of LCY (and I don't think they do) Moscow DME would be improbable, as the UK-Russia market is still tightly regulated, and the Russians would never agree to anything that didn't give at least an equal advantage to their own carriers. Not a competitive approach, but at least they look after their own. Always have done, always will do.
The list of routes suggested as likely to do well unfortunately contains too many points which have failed in the past.
LCY only does well from major business destinations, inbound early morning, outbound afternoon/evening, so not for aircraft actually based at LCY. Everything else is a filler that hopefully covers its direct operating costs. If LCY allowed operators to park during the day I'm sure we would see a lot of aircraft stood there between morning and evening. However there isn't the ground space to permit this.