I may end up doing this myself if it's an easy mod, but I thought I'd just put it out there in case it sparks the interest of someone who can do it easier than I can:

Basically the idea is to calculate the carrying capacity of your current companions--either the companions following you or all the companions in the same cell as you--subtract the weight of any equipment they have equipped, lower their carrying capacity by that amount and add it to yours, making inventory management much easier. This seems pretty simple, though I don't know if it would need NVSE and/or a script on each companion. The only issue I can see is that all of your items would get the effect of any relevant perks like the one that halves weight for items under 2 units, but this is not hard to rationalize, since you're the one managing their inventory anyway.

How easy would this be?