When the Jem'hadar ship was introduced via lockboxes instead of the C-Store it was justified by Cryptic telling us that CBS mandated that the only way exotic non-faction ships would be allowed in the game is in small numbers.
Obviously this policy has changed since everyone currently playing this game can get the Breen ship if they run the race for 25 days - and make no mistake, there are going to be a lot of these ships sitting outside ESD and Qo'noS.
So really, it's time the Jemmie, the Galor and all those other lockbox ships were put in the C-Store since there's no longer any credible excuse not to.
Make brand new ships and put them in lockboxes instead.
The Jem ship was not (and as of now, has never been a "true" Lockbox ship); it was introduced as a prize for the Winterfest race (random award vs the guaranteed for the Breen ship) and then was reintroduced with the Doff recruitment pack (first by itsef and then with the Tuffli). The Winterfest did offer the option of buying boxes for more opportunites, but it was not required and did not involve keys.
Also remember that the Jem was introduced under the old owner, so maybe PWE made a new deal with CBS in regards to the Breen ship.
As far as making it a Z-Store ship, it is not a canon ship for FED or KDF, which means it is not a common ship for use (the premise for the rarity of all the lockbox ships); therefore, it is unlikely that any will be provided at Z-Store.