The usual solution is something called E6 which essentially limits the game by declaring anything over 6th level as Epic.
I even seen this taken as far as Holmes as the whole game over on Dragonsfoot
As a big fan of the hex crawl and of low level play I can see the attraction here, its using the familiar and fun D&D game engine of your choice to play down to Earth "realistic" Heroes that feel more like Conan than Goku.
However I think there is an easier way. Limit spells. As I see it the real trouble makers are not high level fighters and rogues or even the blaster mages, but a whole raft of "suck the fun from the game" spells.
My list (taken in part from here) (who also has an excellent TFT page, here)
Mass Overland Flight
Transport via Flames
Transport via Plants
Word of Recall
plus any other spells like these. and while you are at it limit the duration of wall of iron and wall of stone to say 10 minutes (1 turn) per level .If desired you can also get rid of Bags of Holding and similar items and spells like Secret Chest. Heck if you want to take it to the max, ban rings of sustenance, food and item creation spells and continual light too.
When you do this your spell casters become much more mortal, still needing to find shelter, food and supplies. In addition they can't just appear at the adventure Instead they have to travel like everyone else. Time for a Hex Crawl!
Best of all this does not preclude cool travel items if desired, flying ships, magic mounts and whatever.
Also if you don't want to be a total ogre you might still allow a fly or even mass fly spell at 1 round a level or even the regular duration. Even at 20th level its more a problem solver and combat spell then a plot ender anyway.
These limits still allow a lot of creative fun on the part of the players of all classes while getting rid of most of the shortcuts that can take the game in what some might consider too fantastic a direction..
As for the HP/AC issue. Its nothing to be concerned about in old school games (they cap at 10ish anyway ) but Pathfinder DM's may want to create an alternative system. Its up to you.