I haven't found anything. I just assume it's a problem inherent to EUBs, and personally I can live with that.
Soundwise, I find both instruments really similar (I only used the piezo on the omnibass, I really didn't like the magnetic pickup on that instrument), and if you want to try to emulate the sound of an acoustic double bass with any of those instruments, you will definitely have to process the sound with both: the bests results I've got so far is the use of an acoustic bass IR + EQ+ raise the action. In this video, I was just starting to experiment with IR (no EQ used) but the results can be much better with proper use of EQ:
However, the neck, string separation and fretboard radius are way bigger on the Ibanez, so it really feels much more like an acoustic bass, which forces you to think (and play) more like a double bass player than an electric bass player. This makes a BIG difference.
And last but not least, I find the Ibanez way more visually appealing.