In my humble opinion (also being a bassist) forget the 4ths on the Stick bass and go with the Dual Bass Recipricol. Why? You already have basses tuned in 4ths. Do something different that is going to take you outside your comfort zone and will ultimately give you a whole new dimension in your playing. You will definitely increase your creativity by approaching your lines in a new way. The internal 5ths tuning will force you to think and play differently!! I say, forge ahead with something new!! by the way, I'm saving up for a 10 String Grand Stick, that will have that same Dual Bass Recipricol tuning. I was going to go with the SB8, which is a fine choice, however, Greg Howard brought up the 10 string Grand. It will give you a wider range with the two extra strings, and the spacing between strings will be a bit wider. My plan is to have a Roland GK3 installed so I can trigger acoustic bass patches. Oh, my first Stick years ago was an SB8 tuned in fourths... I regretted having had that 4ths tuning, as I was just playing the same old stuff, only tapping. Also, just think of all the new neurons and neural connections your brain is going to make by learning something new!!! Best of luck to ya!!

Therefore the need to have a bass/stick that will allow me to play bass (and guitar simultaneously),

It sounds like you want a full range instrument, Dual Bass Reciprocal doesn't do that.
A single region tapper seems more of a complement to your 10 string than another dual-region 4ths/5ths instrument.

If you ever want to use a very different single-region tuning there is the Robert Fripp/Guitar Craft/Touch Guitars 8 string tuning BbFCGDACD, 6 strings in fifths plus minor 3rd plus major 2nd.
This has the largest pitch range possible using SE strings.

The SB8 has uniform string spacing yes, as it is designed as a single region instrument.

I have always been troubled by the value of the Stick-bass. If you want a bunch of strings tuned in 4ths to function as a bass guitar, why aren't you looking at the NS/Stick? Yes, there is a tonal difference between the two instruments, but when you can tap, pluck, strum, pop and slap with eight manageable strings that is a lot of function. I love my Grand for its range and chordal function. I love my bass for being a bass (5-string fretless).

I had met a couple of guys when I lived downstate in Michigan that owned SB8’s. For many bass players, they want medium to heavy gage strings that the NS doesn’t provide. For some their choice is for optimized tapping without having to learn mirrored tunings. Such heavy-handed players have no use for a hybrid instrument as fingerstyle is preferred on a standard bass. I play bass with a light touch so the NS works for me. The SB8 is a good solid easy to learn dedicated tapping instrument for those with a heavy touch. Not a big market, but they are out there. Nice that Emmett gives them a choice. Without seeing how the OP plays bass I can’t comment on whether an NS or SB8 is a better choice.

I'd say the SB8 is the most underrated Stick model we make, especially if you want the feel and sensation of playing a Stick but with a bass guitar type tuning, Even better might be the Dual Bass Reciprocal (DBR) tuning across the 8 strings. The low B is then the common string at the 5th position, serving both sides (bass 4ths on the "melody" side and bass 5ths on the bass side).

You'd have highest G at the 1st position (toward the player's left when "worn" for playing, followed by 2nd string D, 3rd A and 4th E, all in descending 4ths. Then down another 4th to low B at the 5th position, followed by 6th string F#, 7th C# and highest "bass" string G# at the 8th position, all in ascending 5ths. The concept is 9 strings on an 8-string board.

I feel this is a bass instrument to contend with. You'd have Jaco's melodic bass lines in the right hand and The Stick's more structural patterns in the left, not to mention Tony's pioneering two-handed bass work on just the 5ths.