I read a few days back that the plant spacings given on packets of seeds for vegetables owe more to commercial production than addressing the needs of the domestic gardener and that it may well be possible to plant at a greater density when one doesn’t have to worry about the size of cultivating or harvesting machinery and suchlike.
I’ve been searching without success for a bit more information on the topic, but haven’t really found anything useful as yet other than one video on YouTube that wasn’t particularly convincing.
Sounds like it could be a good idea though, so as I still have some brassicas to plant out, I might give it a try.