Sheet mulching over suckering thickets

Hi, I’m a landscaper in CO focused on doing things the permie way and I’ve got a client with a backyard that’s currently a massive thicket of Siberian elm, wild plum, and buckthorn... all extremely profuse suckerers. They want a clean slate. My plan is to cut it all to ground level, remove all the cuttings so the ground is level, and sheet mulch over the cut stumps with cardboard and a thick 4-6” fine mulch. I’m expecting to get some suckers that conevbqck and push through which we’ll stay on top of cutting next year, but not too many. Has anyone done this for particularly vigorous brush like these? Am I going be cutting suckers coming up for years to come?

Even better, I've found, is to use something durable like old scraps of carpet, laid in well-overlapping layers. Put a cover mulch over it for aesthetics if desired, and leave it for a year or so.  Then move to the next zone and plant up where it was.  This is a slower process, but will give better control than a cardboard sheetmulch. In some cases it is more effective to push the vegetation down flat and mulch over it, rather than cutting it down first.  This can be done with feet, or possibly with something like a weighted barrel rolled over the top.  This is less prickly and dangerous than getting up next to things like blackberries or poison ivy in order to cut them by hand.

We took down a load of wild plums saplings and some small trees this year, we cut them down flat to the ground and we've been mowing the regrowth. They have not been the most vigorous at regrowing, nowhere near as bad as the Sycamores which really refuse to die.

Yes, carpet is probably tougher, but if you forget to remove it within a year (and I would totally forget) things might grow through it and then you can never get it out in one piece. And it is unlikely to be all-natural biodegradable carpet. Cardboard seems more reliably compostable to me. If there are several layers, cardboard should work well for a year and can then be added to on top