This will give the last level trader shop access to ALL shipments in the game as well as ALL junk items. The idea is that your settlements now have enough reach to get whatever they need or your traders know who to contact to get shipments in from prospectors, scavengers, ect. You do NOT need to have one of the special traders like Vault-Tec Rep or Trader Rylee for this to work, only the third tier shop.

Also the last level bar / food stand will sell all available raw meat as well as dog food for cooking, recipes, and creating cages for wasteland workshop. Many places in the real world sell raw meat such as butcher shops, china town, ect. 

Tier 3 clinics now sell all the required materials to craft chems and guarantee that all of the base chems and healing items are available for sale. 

No DLC's are required and this should work fine with any other workshop store mod.