When placing conveyors and branching with a tee (such as combining the output from two processes into one), sometimes the feed continues from one side while ignoring the other for long stretches of time, even when all conveyor directions, etc. are followed. I think it might be useful to have a combiner tee – one that will deliberately alternate which side a vehicle is pulled from if both inputs are occupied. A similar tee for branching outputs (one in, two out) would be useful too.
I was thinking something like a Que section would be good. A “Wait here for open path” kinda thing. you would put it before the T and any extra would wait at it for the next available slot. This would work with more than just two slots as with a splitter T.