House Rule: Ammunition

I've been pondering what to do with ammunition for weapons like bows, crossbows, slings, and blowguns. On the one hand, I really don't want to have to micro-manage the tracking of ammunition (since it's a pain), but on the other hand I feel there needs to be something there to keep them on a parity with thrown weapons (and also so as not to make a mockery of encumbrance).

So, here's my latest thinking:

• Ammunition supplies will be rated as a number of d6. For instance, a character will have a quiver of arrows (3d6), or similar. Note that this is a rough guide to the number of arrows present, not an exact total.
  
• A full ammunition pool is 4d6. Characters may not carry additional quivers of arrows to give an expanded pool. An ammunition pool may be purchased for 1gp, and counts as a single item towards the character's encumbrance.
  
• At the end of any combat where the character uses his weapon even once, that dice pool may be depleted. The number of dice listed should be rolled. If any dice show a '1', the ammunition pool is reduced by that number. For instance, if the character had a quiver of arrows (3d6), he should roll 3d6. If the result is '1', '4', '5', he now has a quiver of arrows (2d6).
  
• If the ammunition pool is reduced to 1d6 or even to 0, roll 1d6. This is now the exact number of arrows remaining to the character. So if our hero had a quiver of arrows (3d6) and rolled '1, '1', '5' (or '1', '1', '1'), he should now reroll 1d6 to give a final number of arrows. And so he finds he has 3 arrows remaining. These must be tracked individually, and cannot be recovered after use.
  
• The above assumes that the character is able to recover expended ammunition after a combat. If the character is not able to do so (whether because he fled combat, he doesn't have time to search, or other reasons), he should first reduce his ammunition pool by 1 and then roll the remaining pool. So if our hero had a quiver of arrows (3d6) and flees combat, he should roll 2d6. If this returns '3', '4', he now has a quiver of arrows (2d6). Note that blowgun ammunition (and also gunpowder weapons) are exempt from this, as they are not meaningfully recovered. Note also that ammunition pools already take this into account.
  
• Ammunition may be shared from one character to another, but always in batches of 1d6. If this results in a character having an ammunition pool of just 1d6, that character should immediately roll 1d6 to determine the exact number of arrows.
  
• If the DM feels that an attempt is being made to game the above system by splitting and consolidating quivers repeatedly, he can declare that all single-die ammunition pools have a single item of ammunition present, and cannot be further consolidated.
  
• If the party is able to loot arrows from a fallen enemy, these provide an ammunition pool of 1d6 per foe. These may be divided amongst any number of PCs, with the caveat that no PC can exceed a full ammunition pool.
  
• All ammunition pools may be refreshed in any settlement where ammunition may be purchased, free of charge. (Expended ammunition pools are not refreshed - the character must purchase a new quiver of arrows to gain a new ammunition pool.)

The net effect of all of this is that a PC should expect to drop from a full ammunition pool to a single die after either 5 or 6 encounters. If it is assumed that a standard encounter uses 6ish arrows, this provides a similar rate to that provided by the standard rules, without the need to track 20 individual arrows (complete with 50% recovery rate).