I decided to go for 2-8 trains and unload each wagon to a single blue belt, allowing for a relatively compact setup. A single feeder line seems to be able to keep 6 of such stations busy (>95% at least in my test), so I use two feeder lines with a lane
balancer in between. Each station itself has a fairly easy setup:
Output via UG belts onto one blue belt per wagon. 8x8 balancer at the end to prevent hanging on one wagon if not all output is consumed evenly. The little contraptions on the left measure throughput and sound alarm if it drops below theshold. I use buffer chests with 3 slots each to bridge time until next train arrives. 2 slots might work as well, but 3 is safer. I use chain signals between the merger and the station entry to keep all stations open. Stations have signals every wagon to let the incoming train start as soon as a train departs.
Station can be made more compact by 'folding' the balancers above the stations, I might have a look at that.
This requires about 14 trains per minute, so it should work with a regular junction after the lane balancers.
*) I do use prod3 modules where useful, just not anywhere and no beacons, so e.g. in yellow science I use 3x prod3 plus 1x sp3.