Necessity/value of using cardboard or weed barrier under gravel shed foundation?

How important is it to use a weed barrier or some kind of geotextile between gravel and ground? In cases when crushed gravel is poured and tamped 6" deep as a shed foundation, on relatively flat ground with some trenching dug in the soil around it and top soil removed.

Site prep

I plan to dig out the top soil (root zone and a couple inches of soil) as the shed will go on a meadow with lots of herbaceous species and some trees. A few Japanese Honeysuckle are on site and very invasive, but I have uprooted (I think) all of them, or at least cut them down to stump/root.

Materials

I prefer to use minimal plastic or material that cannot be reused or safetly biodegrade (wood, metal and screws). On top of crushed gravel gravel 2" diameter and smaller, the 8’x14′ shed will sit on 4"x6" of larch separated 16" on center, with larch joists and then a moisture barrier below hemlock planking. The field in front of it will be mowed and behind it is Japanese Honeysuckle thicket that will probably try to grow into the shed.

Ground barrier

Cardboard seems like a decent barrier for the weeds maybe lasting ~2-3 years, long enough to kill off what roots may try to grow back that are already under the shed. I figure I will tamp the soil that is dug 2" down all around, lay cardboard, then lay 6" of gravel (or I could lay more). How will cardboard rot under a shed? Is it likely to help or hurt its chances of settling, as it protects gravel from sinking into soil but maybe only for a short period?

I also saw this material as a ground barrier but I don’t think it would help much with a shed. Maybe better than nothing, but not helping distribute the gravel weight to avoid settling:

http://www.dewittcompany.com/Garden_Weed_Barrier_.aspx?productid=66&categoryid=21