I'd like to see a feature supporting multiple accounts. By all means, feel free to make this low priority.
As discussed at Using multiple accounts (ethically), there are occasions where it's legitimate to have multiple IDs, to avoid attaching a real name to discussions on client security or project management issues.
It seems that there's quite a few technical obstacles to overcome to avoid merging, which could be bad - e.g. if I'm discussing a security flaw related to a client project, having all my posts from my pseudonym end up attached to my real name would be very bad.
V1: As long as the link between accounts is only visible to a very restricted group, I'd be happy with explicitly linking (it means any abuse for self-voting is easy to detect, and that self-voting on unlinked accounts could be more harshly dealt with). The only effect of the link would be to prevent merges; rep etc. would remain independent.
V2: Less ideal, but workable for me, would be an option to tag a post (Q or A) as 'private' so that the real ID wasn't visible to anyone other than the chosen few.
By very restricted group or the chosen few I'm referring to the SO team, rather than community mods. This is both an exercise in due diligence, and a recognition that while a mod is generally a responsible member of the SO community, there are no guarantees that they all are; in much the same way, voting for a politician doesn't mean I'd share my clients with them.