Haven't used the Delta3 racks myself, but have sworn by the Cooper B-Line "Access" series for years and years now. They are super easy to use, available in a mind-boggling range of configurations, and don't have annoying corner posts.
In terms of managing the third parties that go into your racks, and you're able to afford it in your business plan, best thing to do is set aside a cabinet or part of a cabinet purely for terminating circuits, which are then patched to your equipment. The cablers then have no business ferreting around where your active equipment is. One of my out and out pet hates is circuits delivered as just flying tails with plugs on the end, left hanging in a hapazard manner around the cabinet, with no proper termination or strain relief. Cheers, Mike
