What happens with planets that fall outside of the collection areas of your trade bases?
Say early in the game where you've only got a trade range of at most two - and you'll start with a trade range of 0. Do all planets start effectively in the core sector until a trade area spreads over them?
What happens if a colonised planet is in sector A (being 6 jumps from a full trade hub), and you build another trade hub 2 jumps away and then raise the trade range so it overlaps the colony? Does it stay in sector A, or does it move to the trade hub it's now closest to?
Trade routes are nominally trade hub > capital, but you can already designate them to go hub > hub > capital should you wish to, which is close to the sector > sector approach.
What happens if a sector has no planets though? If you've set a trade hub up in an area with a lot of free-floating trade but no colonised planets, how does that work?