Help with morning glory remediation

I am trying to determine the best approach for remediation of the perfect nemesis weed trifecta of morning glory/horsetail/creeping buttercup in our front garden. After talking to a few landscaping professionals, we are doing a complete re & re, using a mini excavator to remove the top layer of soil, and most of the existing shrubs. We are improving the drainage, backfilling with good topsoil, laying weed barrier with X holes only for plantings, then mulching thickly over top. This plot borders a large cedar, and a mature cedar hedge, so we will still be pulling MG as it is forever in the roots along one side of the garden where we cant get at it, but are trying to do this right the first time (we inherited the mess when we bought the house), to mitigate the amount of future work.

Questions:

1) How deep should we scalp the existing soil to get most of the MG roots? I am wondering if @ 1 ft. deep will be enough? I know they can run incredibly deep on the mother plants, but what is the best practice generally in this regard?

2) What type of weed barrier will stand a chance in this scenario? I was planning on using the heaviest duty professional grade water permeable product we can find, but my landscaper friend said with mg you must use heavy black poly, as they will break through anything else in a year or 2. I am concerned about the water impermeability issues of this approach however, as well as potential negative environmental effects as the poly eventually breaks down. (Am an organic gardener).

Any advice appreciated! Thanks in advance.