dcollins said:
Of course, that feeds into the whole issue of whether off-book items are really covered by the core rules or not...
Actually, it doesn't even touch upon off-book items.
A found Longsword +2 has a caster level of ... [checks the book] ... CL 6.
A wizard adds the Flaming ability to a Longsword +2. So, it has a caster level of ... [checks the book] ... Huh. Does it have a single CL of 10 - the requirement you like from the Flaming enhancement - or does it have a CL of 6 for the Enhancement bonus and of 10 for the special ability?
If it doesn't change, then if I supress the Enhancement bonus with a targeted dispel magic, it loses the special ability as well.
And I think that's where we'll find our answer, actually.
When you cast a targeted dispel magic at an item, you roll a CL check against the item's CL:
SRD said:
If the object that you target is a magic item, you make a dispel check against the item’s caster level. If you succeed, all the item’s magical properties are suppressed for 1d4 rounds, after which the item recovers on its own.
Note the singular usage of caster level. In other words, you do not roll a dispel check against each property of an item. You roll a dispel check against the entire item, opposed by the item's single caster level.
Therefore, all items have a single caster level and, using the example above, a wizard who adds flaming at CL 10 to an extant +2 Longsword "updates" the CL of the +2 part to 10 as well.
Therefore, any item which has multiple abilities must have all of those abilities operate at the same caster level. In many cases, the cost to do this is non-existant. In some cases, however, it can be very expensive to do.