When we play we make shit up, imagine it and share it with other people. Other people then try to imagine the same thing. Most of the time it's not going to be very similar but most of the time it won't really matter either.
"You're on a boat." is one of my favourite examples of this. You're probably not imagining the same boat as I am. We might not even be imagining any specific boat. Maybe in my head it's a schooner one moment and a luxury yacht the next. But that bit ("on a boat") still carries enough implications, context and limitations that we can act out whole scenes without really needing more. Often we must specify, inquire, describe in more detail. But not that often.
There are, however, moments when the "physicality" of the fiction matters, especially when it comes to making important tactical decisions. Videogames have far outdone us on this front. Thief, Deus Ex, Half-Life etc. all allow us to take advantage of virtual physics, light, sounds, materials, reflections etc. If you play Thief - avoiding the loud clanking metal floor, scuttling across a soft carpet and hiding in the shadows behind a pillar, heart pumping when the guard is just inches away from you - it all has a tangible "physicality" about it. You're aware of your position in a 3D environment, your presence in it. Doing that in a tabletop game is really really hard, possibly a vain enterprise.
How many times has it happened that the GM has described a feature of the landscape to you and you had to go back and forth for a while until you finally figured out how things "really" looked like so you could then make the best decisions based on that? What's the best path to that bad guys camp? Where should I hide myself so they won't see me from over there? It can take a lot of describing and re-describing and sketching.
How many times have you trudged through descriptions of empty rooms or corridors or boring streets, picking to go left or right before you finally arrived at your destination? It gives the world a sense of physical space, spatial relationships, yes. But we're not videogame engines. We actually suck at it. Describing for minutes the journey through a dark forest doesn't really give my players the feeling that walking through a dark forest would give them.
I believe this ties in with my old arguments about immersion. Immersion is not something you do, but something that's done to you through the medium of language. Cues, rhythm, style, careful choice of words, show, don't tell. A kind of poetic (but not lyrical) language.
It also ties back into my old point about representation. In the theater, in old videogames, in old cheap shows the props are obviously fake, the graphics suck, the special effects suck. But we buy it. We buy it, we get drawn into it because there's a narrative quality to it, a rhythm (again). There's nothing real about how these things represent reality. Kids got seriously creeped out by monsters in Dr Who even if they were obviously made from tin foil. My character in an old videogame can be an ASCII sign, but I treat him as real, independently of his visual (graphic, physical) likeness to reality (which is next to zero). The difference between what's apparent and what's actually going on.
So that's my conundrum. I don't really know where to start unraveling it, but I've got some ideas. What I'm talking about is the shift from "physical" maps to "poetic" ones. We don't need to know how many miles there are from Madeupburg to Nonexistantville, we need to know how long it takes and what if feels like. Counting hexes or measuring inches is a needless step to figure out the duration of the journey. Draw a map based on the relationships between places, not its accurate physical properties. Annotate it with atmosphere, not geographical traits.
As a GM I've felt this failure every time I've tried to take the players through a maze. Mazes are friggin cool, mazes are awesome. But in play, they just fail ("the corridor goes on for a while, then it splits left and right, which way do you go...?" ad infinitum). That's because as a GM my first (mistaken) impulse is to draw an actual physical map of the maze and then (poorly) describe to the players what they see as they aimlessly navigate it. To use videogame jargon: we need to become better level designers. But our medium aren't 3D engines - our medium are words.
Push the graph paper and ruler aside. Grab a novel and a dictionary.
So, ok, that was a rant which means joesky tax.
Genre-promoting GP for XP houserule
You would probably need to tweak the numbers for your favorite edition anyway, so I'm not including any. Gold = XP is great because there's a ton of ways of how you can make money, most of which don't include any killing (which is dangerous). But genre heroes (Fahfrd, Conan, Cugel...) are almost always permanently broke. We need incentive to spend monnies, not just pick them up. So now XP = GP spent, but...
Spending GP on normal everyday stuff needed for survival like food and lodgings is standard 1:1 exchange. But you get a 5, 10 or 15% bonus for spending gold on class-appropriate stuff.
Clerics: giving to the poor, donating to churches, building shrines -> personal temple
Fighters: carousing, training, military stuff (weapons, armour, mounts, siege engines) -> castle
Thieves: gambling & luxe, black market goods, bribery -> guild
Wizards: ingredients, books & scrolls, experiments -> wizard tower
OR You can have four gauges tracking separate xp for each class. So a fighter that starts suddenly giving tons of money to a church can get cleric-y powers or become a paladin. A thief that starts investing in books can learn some spells. A monetary investment based multiclass system!
If you have demihumans: Dwarves get XP for NOT spending money but adding it to a hidden hoard somewhere. Elves...I don't know what elves do with money. Maybe they melt it down and craft jewelry with it.
Fit the specifics to the XP math and classes available in your game.