I really like the news of a DLC for this game and the Tinkers are by far my favourite minor race which is mostly due to their standout art but may also have something to do with the fact that they are very useful war assets with high manufacturing value and no moral
That being said I think there is enough room for new races so that there is a good verity of minor and mayor factions. The combination of production values and special traits enables the creation of many new races.
But if a minor race needs to be made a mayor faction, I am glad the Tinkers are the ones who get the treatment
Suggestion: The announcement lore already hints towards the possibility of bumping into some of their colonisation attempts: recommend that these should not be colonies, but rather a unique type of vessel that carries tinkers (a mobile base if you will). Now using the base even after it has been occupied might be too much work if it is considered as a ship so either:
1. Dissolve the ship upon occupation and assign the player the resources it contained (moving the pop right to a planet would be tricky though)
2. Handle the "Colony ship/base" as a sort of planet in the system view. It can only support a small number of districts, only has one biome and is only ideal for Tinkers, but for them it is optimal, and when it is attacked it can defend itself better then normal planets would (more defines hard points)
Also: in accordance with the lore, the Tinkers should have the lowest science and minimal to no food production so their high manufacturing output is balanced out