1. What makes you assume already that a Warden conflict in the North would be a major thing?
2. Even assuming it is and, hypothetically speaking, they actually plan on making HoF a major part of it (which they most certainly won't), why should cater only to those whose HoFs have died, instead of catering only to those whose haven't? What makes the people who chose US ending more eligible to have their choice catered to with a random Warden character rather than those who chose any other ending?
Just because some HoF fans have periodically asked for their character's return, does not make their wishes any less important than your own. In fact insisting so much that the HoF not be brought back while berating the ones who are asking for him to be reintroduced in some major role for going on about it, smacks of borderline hypocrisy.
The reason they aren't bringing back the HoF isn't because a part of their player-base chose US, or a part chose to romance Zevran or another chose to romance Leliana or any of that. It's not even because they can be elven, dwarven or human or ever because they were an unvoiced character. It's a combination of everything.
The point being if at all some day they do manage to overcome all the other hurdles, the 'issue' that some people chose the US ending, is really going to be a non-issue, just like people killing off Oghren or Leliana hasn't mattered up till now save in the Trespasser epilogue.
...and the point soars right over your head. If they just leave the HoF alone, they're not catering to anyone, they're telling the story they want to tell. Sorry that you can't let go, but others including myself have, and not all of us had an US ending, although I did.
Some chose to redeem Loghain, some chose to kill Alistair, others got ninja'd out of the kill by Alistair, see a romanced Alistair for an explanation; he'll show up and take the killing blow. Sure, some did the DR too, but tell me, of all the possible scenarios for a surviving HoF, which one should they use? The one you took? The one Player X took? Because you can bet if they don't pick the "right" one, there's going to be an explosion on here. It's far better to just leave it alone, and use a new protagonist, there's no backstory to worry about as far as the PC goes, and yeah, there's gonna be plenty of "But it should have been the HoF" running for at least 4 years, I mean, let's look at release dates realistically here, and we still have people going on about "But it should have been the HoF". It's better to leave the people that are already mad that their Wardens aren't the most important people in Thedas any more mad than to aggravate a whole new segment of the fanbase for "doing it wrong", which for some may even mean "doing it at all".