For the sake of the debate, can we at least acknowledge that while some people may want a through service and prefer that, it does not mean a majority prefer that option. It also does not mean the option to change at OOC should be discouraged either. This through service argument can also be flipped: many people value their time far more than sitting on a packed 4-car Voyager for an additional hour, and many people make a change of train for many routes without a problem.
I get that some people may worry that their nearest mainline station may lose long distance direct connections, but if a significantly large enough number of people transfer to HS2 for whatever reason (it may be cheaper, and more frequent, not just quicker), then there is a risk that an existing direct service may not be the best use of capacity. Other services that have demand could use that path that are prevented from doing so by the existence of long distance trains. Rather than two Cross Country services between Manchester & Birmingham, I suspect there will just be one (perhaps to Bristol), with the Manchester-Bournemouth service split in to a Bournemouth-Birmingham Moor Street service and some additional stopping services feeding in to Manchester & Birmingham. It will be the frequency, speed and OOC that facilitates this.