I understand that your multiple unit of measure functionality is still not that useful and a major investment to improve.
However, you don't need to reengineer the whole product to still deliver significant benefits to the food and beverage industry.
Instead since you already capture the weight and the weight unit type for items, you could allow the following via a preference switch:
a) show an additional price per weight unit of measure in sales and purchases lines, along side the unit price. In many industries prices are discussed and set in this weight unit of measure, rather than the inventory unit.
b)optionally allow you to set pricing in items by that price per weight unit, rather than the inventory unit.
c)advanced bonus points for having a different sales and purchasing weight unit of measure for pricing. i.e. purchase prices are set per mt and sales price per kg.
You can do this without any change to multiple unit of measure functionality. Its a simple calculation and if the user hasn't entered a weight in the item you just disable that field on the screens and leave in blank in reports.