I've been playing Satisfactory for about two weeks now, watching a lot of videos on YT and just in general contemplating how great the game is and what might make it better (at least from my perspective). Here are a few ideas of mine that I have not yet seen suggested or described in a way quite like how I envision them. I apologize if any of my suggestions have already been expressed elsewhere.
1) Varied storage containers
The Storage Container and its upgrade are wonderful structures to balance the supply and demand of resources and to create retrieval points for items. I would love to see an extra variation on the storage container: a container with the input/output on the same side. This would allow tighter usages of the Storage Container in specific circumstances where an in-line structure isn't what an engineer is looking for.
2) Diagonal Wall Placement
This idea could go along with other ideas I've seen about additional foundation shapes, but could also be treated as standalone. The idea is that instead of having strictly rectangular structures walls can snap together diagonally across foundations to create variations in the dimensions of factories and buildings. I personally don't mind the idea of unused foundation jutting out from an octagonal structure where there would have been flat corners; I see that as necessary foundation for the structure itself. Additionally, this could be used internally to create unique compartments within a building, thus increasing structural creativity.
3) Lockable Inventory Slots
In almost any game I play that features sortable inventory I tend to sort the inventory my own way. In Satisfactory dying, or even absentmindedly clicking the sort button, completely undoes any hand-sorted inventory structure. Thus I propose being able to lock or reserve inventory slots for specific items so that collected and retrieved items default to that slot until a full stack is created, after which items will fall into the first available slot as normal.
4) Manual Placement and Edit of Vehicle Waypoints
Vehicle Autopilot in Satisfactory is (expletive) fantastic. I cant think of a single game that lets you automate vehicles in any manner like I've seen here. But, I think the one thing the vehicle autopilot system in Satisfactory is missing as it currently exists is the ability to manually set and edit waypoints. Defining variables such as minimum speed, max speed, idle time, etc. would give engineers that desire to rely on vehicles for their transport needs a solid set of tools over just using belts everywhere or relying on the currently-in-development Train/Rail systems.
So, those are my main ideas for things I'd like to see considered, and maybe even included, in Satisfactory. I look forward to any constructive criticism and feedback that anyone reading this would like to offer.