It seems to me that while treating as a systematic method of mite management can only result in perpetual treatment dependence, there is no good reason why treatments cannot be used carefully within a proper resistance-raising breeding program.
In established treatment-dependent apiaries this might be part of a 'soft bond' approach. But there are dangers. Here in the UK current official advice is to 'treat only those that need it'. All else being equal that will simply have the result of perpetuating treatment-dependence, as without culling the weak genes will re-enter the breeding pool.
Things are different in dedicated resistance raising apiaries, where a good proportion of stocks are already resistant to a good degree. As long a treating doesn't interfere with evaluation of resistance, there is no reason why less resistant stocks shouldn't be de-queened, the hives 'cleaned' of mites to raise vigour and avoid damaging the new queen/s, and requeened and/or used to make new colonies.
As far as I can see the only objection to this is that it might be useful to have more varroa about to make clearer the varying levels of resistance. But there are problems with this. The mites will tend to enter other hives unevenly, and this might load evaluations in several ways - both good and bad. For example, those with strong doorkeeping will tend not to suffer - and strong doorkeeping is surely a good thing. (Those nearby might be expected to suffer more badly - but then we might attribute a failure to that when it was actually something else)
In all I think this sort of thing introduces complexities that will tend to obscure what it is we want clear. And for that reason there isn't a good argument for maintaining high varroa levels. Hives failing due to lack of resistance to varroa should be 'cleaned' and used to aid more throws of the (loaded) dice.
What do others think?