Khayman said:
This leads to the possibility of expanding item powers with an XP cost (much as one might apply metamagic feats to a spell). Say you need extra damage from your magic weapon, or a few more rounds of flight from your winged boots --- toss in some XP and away you go. An ability possibly restricted to spontaneous casters (such as bards or sorcerers) or clerics with the magic domain.
This is a nice idea. New character concepts are jumping up in front of me ...
I've never heard of anyone lamenting the players overusing magic items that they already have. Usually it's more along the lines of "Help, my players are hoarding their one-shots and charge-using items"
Khayman said:
The problem is in calculating the cost and ease. I'd make it costly, to say the least --- there exists some potential for upsetting game balance.
Meh, balance is overrated
Maybe having a feat or skill rank requirement would provide for this:
Concentration check, DC 10 + caster level requirement to make the item
possibly requiring that the character possess the pertinent metamagic feat.
A cost of item spell level x item creator caster level XP (eg. To
Extend the effects of
Boots of Flying would cost 3+1x5=20XP) might be appropriate.
An alternative, if anyone loathes obscenely the thought of yet another way to spend hard-earned XP, have the character be required to sacrifice a spell slot of the appropriate level to use the enhancement(eg. In order to
Exend the effects of
Boots of Flying might cost a 4th level spell slot and the wearer must have
Extend Spell).
Hopefully there's some wheat in this chaff.