Packs that are smaller than the unit - i.e. decimal packs

A lot of customers have products setup where the "standard unit of sale" isnt the "smallest unit". 

e.g. I sell steel tubes by the metre, but the product is set up to 3 decimal places so that i can also sell in mm. In the accounts system a qty of 1 means 1M, a qty of 0.01 = 1cm and a qty of 0.001 = 1mm. The tubes actually arrive in 5.2M lenghts.

I probably dont want to change all the products in my accounting system just to make packs work.

what i want to be able to do is setup a pack configuration where the basic unit is "Metres" and then setup a pack size of "Centimeters" where the pack qty is 0.01, and "Milimeters" where the pack qty is 0.001. And, perhaps if a standard lenght of this tube is 5M i might want a pack of "5.2M Tube" where the pack qty is 5.2.

We already then sort the packs on the popup window by the "pack factor qty" so, this would be no different. We still do that but the "standard unit of sale" then appears in the middle of the list, eg.

- 5.2M Max Length's of tube

- Metres

- Centimeters

- Millimeters

You then enter qty's however you like (e.g. one customer says can i have 1000 mm, another says one full tube, another says 500mm) and the system works this out as a standard qty (e.g. in these examples 1.000, 5.200, 0.500)