I would also like to add that adding it into the main game would be more beneficial as a whole to the community. If you change it to a mod, that means console players would no longer get to play it. You would lose a huge player base. As you did with vanilla servers, you could host prim+ servers that would pander to the players that don't want access to the electricity and tek tiers. However, you would enhance the largest player base you have by adding it all into the main game. It has to be maintained, work with the rest of the game, and patches won't keep breaking it. This is the best option. Add the collectables, the ore, coal, crops etc. As well as the crafting benches and recipes. You'll add more stuff to do in the game and honestly having a cosmetic option to some things is something this game is missing. (We would pay extra for cosmetic options) The kibble is fantastic but if you add the crops to the main game is adds yet another option to taming and cooking (i love the baking and farming lol) if we're being honest lumber and brick look fantastic and combining them with wood and stone makes the aesthetic building much more fun and the glass just looks amazing.
Sorry for the long run on post but ive talked to my server and this is the combined feedback. There is no drawback to adding prim+ in full into the main game.
I know it would require a great deal of coding and testing but it would be worth it and it's something that a great deal of your players have been asking for. More options, decorations and diversity.