I got an idea of how to smelt ore and load directly on blue belts with some inserter timings, using a total of 6 combinators. It seems to work perfectly as long as there is no back pressure on the belts. 7 smelters with productivity modules and 7 beacons each is just about perfect for filling one side of the belt.
I built 6 rows, because then 5 full belts of ore should match, although I couldn't get full throughput on a 5-6 balancer in my game so I removed it.
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The full blueprint seemed to break the forum, so this is two rows that includes the combinators and the repeating patterns of beacons:Blueprint