In "All Good Things" the warp scale had been reclassified, since the Pasteur
could reach warp 13 (if memory serves), so in the 2470s a ship getting to warp 15 wouldn't be unbelievable.
Regarding the crew: why would you waste so much energy and computer memory for half the crew being holograms (also 'hard light holograms' isn't something Trek has had before, the EMH was able to switch from being solid to intangible at will)? A computer virus or a hacker could get into the system and easily take over half the crew and then the ship with little effort, plus if there was a loss of power then the complement would be halved in a time of crisis.
I also doubt that a Klingon/Vulcan hybrid would need much genetic experimentation when ovarial resequencing made it highly probable that a Klingon and Trill could have children together in 2374, so by the time of your series then it shouldn't be difficult.