I thought of doing the same thing,. I also have a Rogue baritone uke, but do not like it as a baritone uke. I thought it might be fun to convert to a bass, as you describe.
Of course the Kala U-Bass is on a baritone body, so one could even get the actual bass pitches (rather than an octave up) using the U-Bass strings. However, those would not fit on normal tuners and a normal bridge, so one would really have to modifythe instrument substantially, to be able to use the U-Bass strings with it. Also, the U-bass really needs amplification to be heard much.
But yes, I would think it easy to convert to a piccolo bass, one octave higher than a normal bass. I would suggest, however, not using the lowest four strings of a regular classical guitar set, as those would be very floppy on the smaller scale of a bari uke (compared to a full-size guitar). I think the bari uke scale is similar to that of a 3/4 size guitar. So, I think it would be better to buy a set of strings made for a 3/4 size guitar, and use the lower four strings of that set. As an alternative, one could try using an extra hard tension classical guitar set. But using strings from a normal tension CG set on a baritone uke, would result, I would think, in strings way too floppy.