I'm mixed on IDs and think that they might really only be beneficial on a per-thread basis (as in, BVs can switch a thread to have IDs if they want to, off by default). Obviously they help mitigate schizo behavior, but they also create a "profile" for individuals in threads, which I don't really like all that much.
One alternative I like is the (Me) tag. Similar to (You), any time you respond to yourself, the quote will be tagged as such. This doesn't completely stop schizo behavior but certainly helps. Probably not possible without software modification.
Another is a per-person "brand," something that BVs can place on an individual that acts as a retroactive ID within the thread. This might not have much use, since users that would be "branded" probably should be banned outright, but maybe there are situations that aren't severe enough to call for a ban. Just like above I'm unsure if this would require software modification.
It might also be useful to have a "vote" to "brand" someone, but obviously, validating unique votes is more difficult than a simple IP check, and can be abused.