Chris

In most cases those channels' business model is built entirely on repeating stuff, often very old stuff, and their deals for acquiring that content will reflect that. Plus, much of it being old and not especially good, it's cheap. The BBC could no doubt emulate this but would likely fall foul of its own public service test. If it's directly emulating 5USA, which is a non-public service commercial rival, it is doubtful it is acting within its terms of operation.

The BBC could only feasibly emulate the likes of 5USA (which, incidentally, actually just shows teleshopping for half the night, along with many of the other minor channels) by repeating its own content, which is when you rapidly come back to the issue of repeat fees.

This has nothing at all to do with whether it's possible, and everything to do with whether it is practical and cost effective given the BBC's unique position.