Luxuries, the Market and Trade Routes

The idea is as follows: (Bold represents edits)

1. Trade Routes share food along the Trade Route (helping with the excess food problem).
2. Trade Routes only give Dust between your own systems. Faction Trade still gives Science.
   
3. Trade Route Dust income is proportional to food income (surplus or total is the question really), therefore making food more relevant in the late game.
4. Trade Routes gain bonus Dust income from Strategic and Luxury resources along its Route alongside bonus experience.
   
5. Trade Routes do not give bonus Luxuries, rather that Strategic and Luxuries slowly trickle onto the market, increasing based on Trade Route Levels.
6. Spending on Trade Routes changed to "subsidizing", where the XP gains for that TC are massively increased, while also reducing XP for other TCs.
   
7. Luxuries slowly deplete on the market, based on Minor faction count and galaxy-wide System development levels.

This solves several issues here.

1. Helps develop your Lava/Barren systems who don't have as much access to food than a single 6 planet system that sits there with 900+ food income and nothing to do with it besides manpower.
   
2. Trade Route Science becomes an issue that completely negates any early game science bonuses and this deals with any outliers while still providing empire-wide bonuses (food)
3. Basically makes late-game food still relevant besides manpower (which is similar to food in how you either have too much or too little).
   
4. Extending this to include Strategics basically smooths everything out, although a lot of luxuries give bonus food which makes them better.
5. This means that everyone has access to every resource in the game, while still allowing people to monopolize a few Luxuries to sell on the market.
   
6. The idea is that you want to invest in this specific route and so the other TCs fall behind a bit compared to your pride and joy.
7. Strategics are expended while Luxuries in their current state just aren't. This will hopefully try to reduce the total amount of luxuries on the market to otherwise make sure the demand is naturally variable. It also makes sense that stuff like Redsang is being used.
   

Further down the line you could also give more faction specific traits and make new events around this system fairly easily. Riftborn are the counterpoint to this, but Riftborn are heavily isolationist so I don't think they should really be into the trading game (it's even canon that they have literally no idea what Dust is).