I like the idea. Even if the Devs don't go for combining the factions, Synth foods is in a unique position to generate activity in a lot of underplayed factions.
Planetform: Helped Synth manipulate the environment to gain a market advantage. This opens up RP with Planetform and gives Synth a valid reason to transport the commodities needed for terraforming.
Cryer: Synth without question would be interested in pharmaceutical enhancements to it's products. I can think of a number of shady business dealings this could lead to. This also opens up transport of those commodities.
Orbital Spa and Cruise: Would no doubt be interested in food stuff produced by Synth, given the amount of catering business they do. Also, where else do you think Synth Foods executives take their vacations?
Also, given the unique situation Synth is in being a Libertonian company operating in a house hostile to Liberty means they would have to use outside shippers to import some sensitive items to Stuttgart. Smuggling anyone??
If you add in the commodities needed to produce, package and distribute Products, Synth looks like it has enough legit commodities to trade. Although, I still agree that there NEEDS to be a trade route with paste that goes through the Farmers primary ZOI.
All in all, Synth Foods could be a VERY deep rabbit hole.
Gateway could deliver imported goods from Liberty to Stuttgart with no problems. Why use smugglers to do what could be done easily through legal means?