I keep thinking of how one sprouts seeds on a small scale and if it can be scaled up to meet your needs. I use a jar with cheese cloth over the mouth and daily fill with it water and then dump it out through the cheese cloth lid. Could this same principle work on a large scale? With, say, a 55 gallon barrel with a rod inserted through it so it can be spun around almost like a compost tumbler. Or I guess you could use an actual compost tumbler with sections cut out of it and covered with fine enough mesh to drain the seeds. Mind you I have no experience doing this, it was just the idea that popped into my head when I read your post. Good luck and let us know how you do it and how it works when you get there, cheers
This is my favorite video on youtube about microgreen sprouting. Jolly from Cross Family Farms once told me that the grow beds shown in this video were made by her father for $1000.