So I was like thinking of a way to slow down how fast the market is destroyed by breeding because even when new pokemon are added we will still have the same issues.
In this new egg group things would work slightly different, Let's say a new pokemon called Goalupadoop is in this new egg group. Goalupadoop will only be able to breed with other Goalupadoops and also Goalupadoop can learn many bad ass leveling moves and/or eggs moves. That way the use of people's 6x31 ditto will be rethunk (lol) Also these new pokes could each have very low and high gender rates based off which tier said pokemon is in, Like if Goalupadoop is Uber derp derp then it would have a low female hatch rate he could also only show up during swarms at night even and you can only catch him with a nest ball! (okay that's a little much)
You could even do small egg groups of say like 5 pokemon that are all dog like pokemon. This could also be a way of bringing in new pokemon like mudkipz!
Also Double EXP and EVP weekends ftw