i've pondered this same question for several years, but had yet to find something to my satisfaction, until recently. just as a foreword, i really liked the idea of h-bars (for some extra nice/expensive ones check out: http://www.jonesbikes.com/h-bar.html
), but also really liked riding on the hoods. i never spent time in the drops, no matter how bad the head wind was, in part because my hood position was about as aggressive a position as i could sustain.
flash forward to my recent IGH (internal gear hub)conversion, and i also needed a bar that could split in the middle to mount a grip shifter. i thought about going the aerobar/TT route, and even chatted with some guy in a local club about his set-up. but when i rode with him, he spent about 5% of his time on the aero bars, and the rest on the flats, making wonder why he bothered to attach the things, except as a conversation starter (YMMV of course). at the same time i stumbled upon a crazy bar similar to the h-bar at my LBS made by the local company Bike Friday, better known for their somewhat eccentric folding bicycles. the bars, a BF "STI-bar," are designed to replicate the riding-on-the-hood feel, and just so happen to enable a twist-shifter by coming apart in the middle (99% of riders won't need this, of course).
you can see pix of my set-up here:
the feel is about 90% similar to the hoods, at the moment. the geometry/ergonomics are identical to my hood-riding position (i planned it this way), but the bars as they are currently wrapped do not replicate the over-squishy sensation of brifter hoods. in other words, to more faithfully replicate it, i need to add a little more squish (i.e, padded tape) to the horns. on the other hand (or two hands), i lose the useless drop portion that i never used, and do find a truly flat section of the bar to be quite comfortable, though for speed cruising i am still back on the "hoods"/horns.
lastly, because it was a question for me, too: the seam in the middle of the bars (where they come apart) is a non-issue for safety. i used red loctite for the final assembly (which my resident engineer assured me was overkill), and then clamped to torque specification on my stem. afterward, no matter how we yanked they did not move (and we really honestly tried to move them). another note: i had the bars cut to 40cm to match my drop bar width; the BF bars weigh a touch more than the seamless drops they replaced, and cost $65, which isn't cheap, but for my needs was the only elegant IGH solution. you can see a rather poor picture of the BF bars at: http://community.bikefriday.com/faq?question=1710
good luck, and let us know if you find another solution, or if you go with one of the bars you mention in your original post!