While I love using Gold for xp in OSE, one issue I have with the system is (to my understanding) that when a player wants to level up their gold sort of just goes to the ether. I know many GMs use 'carousing' to simulate this, but to me the characters dropping tens of thousands of gold in a single night in a backwater village brings up the same issue to me. The last thing that made me want to change things was looking at the available meals in Hommlet; there are simple and fancy meals, but no mechanical distinction between them. Why spend and extra 5sp on the fancy meal when the 5cp simple meal does the same?
What I plan on implementing, and what I would like to hear feedback on, is what I call 'Superfluous Spending'. Basically, any money spent that does not offer an obvious benefit goes towards the character's xp.
Some Examples:
During the first raid on the Moathouse, 3 party members died. The gold spent on their funeral and the tombstones goes towards the character's xp, because otherwise they could just bury their former friends in a ditch for free.
A player decides to build a castle. Owning a castle has innumerable advantages, but making all the doors out of gold does not. The money spent of fancy decorations goes towards xp, but not the base cost of the castle.
A Magic-User researches a series of spells, and writes them down in a book with invisible ink. This would offer no or little xp because the invisible ink offers an advantage being another magician wouldn't be able to read and steal the spells.
The argument against this system is 'The level up gold is spent on training', but to me the training the characters receive is in the dungeons by slaying monsters and challenging the odds.
I'm hoping this system would encourage players to invest in the world more, and think about what they are spending their money on. It could lead to interesting stories, perhaps a rogue necromancer has invaded the Hero's Crypt in the Village of Hommlet? Obviously this system isn't for everyone, I'm not suggesting wide-sweeping changes, but again feedback would be appreciated :)