arg :-X
I have a five-year rotation master plan for five groups: nightshades, roots, allium, brassica/orientals/'weeds' (like rocket & spinach) and 'wild cards' - sweetcorn/squash.
I don't grow many spuds, so including them with toms makes sense for me, nor much brassica, so bundling them in with weeds and herbs made sense to make the growing areas for the five groups roughly similar. This bundling gives me six beds per 'group'. Sometimes it gets a little out of kilter, but so long as there's a two-year gap, or I don't do anything daft like forget which beds have white rot, it seems to work OK.