After reading  The Pen is a Sword: The Blood Books on AO3 by A_Being_Of_Violet_Fire not long after reading several Eureka fics this came up

= Harry & Percy forming a solid friendship and eventual relationship behind everyone backs, as the overlooked ones, that leads to them fully escaping wizarding europe, after draining the Potter/Black vaults/properties of everything valuable, for the Magical/Supernatural/Intellectual sanctuary of Eureka

Both gain full asylum/citizenship, new Identities, tailored in-depth magical & mundane education, medical & healing, weekly therapy{not Barlow}, purification ritual, their secret dream jobs{opposite expectations}, true friend/brother/dad in Nathan Stark, birthrights, makeovers...

Eventually they have three sons together{mpreg or surrogates or adoption} that don't get subjected to the Dursley or Weasley version of parenting{abuse, overbearing, neglect or comparing kids}

Harry ends up forming a solid friendship with Jack Carter when he arrives in town, helping him adjust, stay sane & keep his secrets - Keeps him sane after Percy dies the year before

Main Crossovers = Buffy, Charmed, Supernatural

What If Xander had a brother who died before Jesse & Xander reacted by extensive training so he could protect himself, his platonic soul mate Jesse & his emotionally stunted step sister Willow – however after Jesse death he moves from defence to offense and starts nightly hunts & mapping out the various lairs, nests, caches, deaths...etc so he can regularly hit the hot spots

Leads to major conflict with the overbearing & willfully blind special syndrome gang = Willow{conflicts with her fantasy version of Xander}, Buffy{wants to subject her version of normal on him} and Giles{impractical snobby researcher & council lackey}

Training = Supernatural, Self Defence, Demonic, Tracking, Weapons, Paranormal, Strategy, First Aid, Thieving, Magical...

Bonus Points if Xander is a part of an old & unique natural born witch family that has hunted ALL styles of demonic/supernatural/paranormal/magical threats, something which is reflected in their comprehensive book of shadows = leads to him having Leo as his Whitelighter/Mentor, a supportive power{empathy or Sensing evil} & a highly destructive active power{energy blasts-pyrokinesis-molecular combustion-energy waves-advance telekinesis-energy balls-molecular dispersion...}

Bonus Bonus Points if Xander is shown as highly practical, knowledgeable, competent, proactive, realistic, perceptive, blunt, driven, strategic...

Triple Bonus Points if Xander has protective tattoos against all types of possessions, non healing magic, psychic manipulation & impersonations{skinwalkers-shapeshifters..}