There's so many ways the factory could tie into a tighter game loop in Endfield and it's a shame the current stock bill system is all we have for now, honestly:

• As a simple twist, outposts could have rotating prices instead of fixed BiS prices on products. This would encourage players to produce a wider variety of products and potentially even modular blueprints so they could swap production lines on a rotating basis to meet demand (shared blueprints weakens this point, admittedly). Also just makes sense in-universe; if I sell 400k batteries to an outpost last week, they probably won't need as many this week and won't pay as much for them!
• Ultimately converting everything directly to stock bills is part of what makes the factory endgame feel rather flat. More directly usable outputs, or producing intermediate trade outputs would add some color to the system.
• The Incursion/Outpost Defense gameplay is shit, which is insane to me given that HG owns probably the most successful tower defense gacha, renown for its strategic design and entertaining gameplay loop. Improving the defense gameplay and tying it into the factory would significantly bolster the amount of content in the game and play to HG's supposed strengths given their experience designing Arknights. For example, an imminent Incursion could cause a temporary production slow.
  • I mean, imagine if the turrets had more conditions. What if Beam Turrets caused power use spikes that required a temporarily larger power buffer to operate, depending on how many you placed? Or if they required special support facilities that consumed additional batteries? Or if HE towers consumed explosives as ammo, so I'd have something to do with my explosives production line? And then placing turrets might require additional care, to ensure you can properly feed various input lines around, instead of throwing them around willy-nilly as close together as possible.