The main problem you're going to run into with those drop bar ends is that if you mount them on the ends of your handlebar you end up with a ridiculously wide drop bar and if you mount them inboard of your brakes/shifters you end up with a ridiculously narrow drop bar. I think that's even more of a problem than that you won't have access to your brakes while in the drops.

I'd be more inclined to use some long normal bar ends positioned near horizontally to let you stretch out into a more aero position. You could even try installing those inboard of the brakes/shifters to allow a narrower position, but that might make the handling twitchier than you'd like.

If you're more worried about comfort than speed, I think there are better solutions. Maybe even try a trekking bar.