I know total utilitarians who'd have no problem with that. Imagine simulated minds instead of carbon-based ones. If you can just imagine shutting one simulation off and turning on another one, this can eliminate some of our intuitive aversions to killing and maybe it will make the conclusion less counterintuitive. Personally I'm not a total utilitarian, but I don't think that's a particularly problematic aspect of it.

My problem with total hedonistic utiltiarianism is the following: Imagine a planet full of beings living in terrible suffering. You have the choice to either euthanize them all (or just make them happy), or let them go on living forever, while also creating a sufficiently huge number of beings with lives barely worth living somewhere else. Now that I find unacceptable. I don't think you do anything good by bringing a happy being into existence.