Were you able to complete this job for the client?
We have a similar requirement with our Shopify store reimagineco.ca
We have some products that are sold in kg and we need customers to be able to order, for example, 0.235kg. It won't work to make all the numbers into grams, because the quantities in Shopify need to sync with Vend POS which is our in-store POS system. In store our quantities are in kg, so it should be the same way in Shopify. However, Shopify only allows integers for the quantity field.
Please could you let me know whether you could do this, what the specs and price of the job would be, and when you could get this completed?