The wager

I've had an idea about a process to allow characters to do heroic feats during the game.

For most things, I intend to use the following scheme:

• If something is not particularly hard, a character can just do it.
• If something could be done by an average guy about half the time, roll d20 and get equal or less than the appropriate ability score. Example: push open stuck door, d20 roll STR.
• If an average probably couldn't do it, but might get lucky and pull it off, roll d100 and get equal to or less than appropriate ability score.  Lift portcullis,  roll d100 vs. STR.

So far so good.   But, what if the player wants to try something odd.   Here's where "The Wager" comes in.  The character  proposes a wager.   He offers up some negative consequences in exchange for a chance to do something outside the rules.   The DM has to accept the terms, and then a roll is made.  On these wagers, PC cannot spend Fate Chips for re-rolls, ever.

Example:  player wants to throw a dagger to cut a rope.  This is virtually impossible.   Proposes a wager:   "I'm using my +1 dagger, If I fail the throw, my dagger flies out of sight and I lose it forever.  Since the player is risking a magic item, DM rules that he can make a d20 DEX check to succeed.  

Suppose he doesn't have a magic dagger to risk.  He could wager a "Fate Chip" instead.   Since these are much more common, DM might rule that this is  a D100 DEX check needs to be made.  If this seems too unlikely, the PC might try to up the wager to 2 Fate Chips and the character will fall down and loose a turn if the check is changed to a d20 DEX.