TLDR version:
A stackable/connectable Input/output unit.
Unlocks at Tier 7 (This is the point where you will likely start making much more elaborate factories because the construction chains become more complex).
About the size and shape of a splitter/merger. 1 input & 1 output on opposite sides.
You can build 2 units right next or on top of eachother where they connect and form a bigger I/O unit with 2 inputs and 2 outputs. Add another unit and y ou have 3/3 (you don't have to use all inputs or outputs). Belt capacity outside of the unit still counts. Not inside the unit (just like a industrial container).
All input is "pooled" and equally distributed to all connected outputs (just like a regular splitter does now).
Price: I have no issue with this being an advanced unit, requiring a hefty price.
5x the unit price of a programmable splitter should make this "hard enough" that you would only use this unit once you have the basics in place to even have a real need for it (5 heavy modular frames, 5d motors, 5x supercomputer)
So this would:
This would solve a lot of the requests for other changes to splitters and mergers.
It would solve the balancer issue (because it will balance to all outputs), even if this wasn't my goal.
It would handle belt full condition and input issues a lot easier.
It makes large production facilities a lot easier to build, maintain and upgrade.
Help with fps rate because you don't need huge setups of hand making a balancer/handler with regular splitter/mergers.
Motivation:
I've been opposed to the idea/suggestion of load balancers since I'm not convinced they are needed. I find proper overflow handling of much more importance than "balance". My negative view behind "balancers" is that balance is a moot point anyway if you then branch off and feed multiple facilities having different usage rates. I have not yet seen a "balancer" that properly handles cases where 1 input stops, or where 1 output is full.
So I can make everything I need out of regular splitters and mergers just fine, but working (in early access) on my upcoming aluminium facility is getting me in a bit of a pickle.
I have it set up as 6 lanes (because of belt capacity I need to split it up) of silica production (6x10 assemblers, but planning to add a 2nd floor for 6 more lines of 6). And 6 lanes of ingot production (also planning to add a 2nd floor).
The problem with these overflow handlers and balancers and such... They become exponentially more difficult as you add more inputs and outputs. And while fun to design and even build the first one... it gets tedious on the 2nd... and the 3rd... and...
Upgrading my 6 input/6 output handler (2 of them) into 6 input 12 output will add a ton of extra complexity, build time, and huge amounts of belts snaking around. This isn't going to be good for (my already bad) framerate.