One Product sold in different weights

[ghardin]

Joomla 3.7.2
VM 3.2.2
My client has a product they sell in 4 different weights.  All products sell at the same price per pound, $5, but different shopper groups get different price levels.  So the 1.5lb pkg sells for $7.5 to the default group.  We know we can set these up in a parent child configurations, but the problem comes out when the client needs to change the overall price per pound.  Then they have to go thru each child (as many as 7 right now), recalculate the child prices for each affected group. 
Setting this up as a simple variable list on a parent item works for the pricing part, BUT then the shipping weight is not calculated for the various options and shipping charges are not correct.

Does anyone have a way to set this up using multivariants where one variant could care the Product name, the price for that option and the weight?  Then the pricing could be simply adjusted (competitive pricing is critical) on the parent and the variants are a multiplier (+ or -) of the price level per shopper and the shipping weights would be correct?

Is that possible and how might it be done?

[Milbo]

You just remove the prices from the children and set the price only for the parent. Set different weight for children. Done.

[ghardin]

Thanks Milbo, that will work, but we were hoping to eliminate the need for child products.  They still need to be maintained for images, descriptions, inventory of each package type and shopper group pricing.
I found a plugin here on the forums, http://forum.virtuemart.net/index.php?topic=127362.msg436572#msg436572, that does most of what I need.  It has a few shortcomings, but generally is a good solution.  It would be nice if VM3 had this kind of custom field that would allow for formulas.