Shoot some b-roll on spec, maybe? I agree with having shorter (30-40 second at longest) and specific reels for different clients. You don't need a lot of b-roll to make a 40-second reel, which is all most clients will watch anyway.
I have this same problem. Have done a mix of stuff and my reel doesn't cater to any particular audience, but I don't have enough for four different reels yet! Haven't gotten any work off it since I cut it, only work based on owning a camera, but I haven't really been trying that hard lately:DP Reel on Vimeo
For this year, I'm cutting more like you suggest... three or four short, targeted reels and links to footage I've shot that I have clearance to post. But I think just interviews is a bit limited; I'd find some basic b-roll if possible. Find a crane and shoot a couple establishing shots, do some simple some time-lapse, just look at corporate reels and what b-roll they have and then copy five or six shots. Put some music so the words themselves become irrelevant and if you don't have enough b-roll throw some titles in. Shooting for any particular genre is a Catch 22 unless you network feverishly or have connections... if you need to shoot on spec, shoot on spec but do it smart.