It's something I pondered a bit as I look at TSR settings I'd like to run, while Hyperborea has easily become my preferred ruleset. Do I tone stuff down to Hyperborea scale, or expand out? It's easy enough to port over the basics for levels 13+ from 1e, there's just a few points of AS&SH rules that you'll have to judge on, for instance FA is capped to 12 (3e RM pg. 19) and saves cap out at HD 17. Should those advance further, or do you leave them as-is? If you do leave them, does giving spell-casters more spells per day/spell levels tilt the balance too much in favour of casters? What about thief abilities? Should those end up capping out at 10:12, should you advance up the dice chain (to borrow a DCC-ism), or just allow for thieves that are so good at what they do it's basically supernatural? I think once you make your decisions about those, you're pretty much good to go.