That's actually something I've been trying to figure out, which could also work into this situation. Mostly for recording ideas at home, since I don't play guitar, I'd like to find out how to make a bass sound like a guitar. There are some all-bass bands who've done that. The only one that comes to mind is these guys:
Switchblade Kittens . Something about not wanting to deal with guitarists' attitudes.
Fundamentally, all he's doing in Royal Blood is splitting the bass signal, with one line going through an octave up (POG, or whatever) and a bunch of guitar effects - creating a typical bass & guitar in unison, like most of the Sex Pistols tracks.
It's been done millions of times the other way around, with guitarists using an octave down effect, to get guitar & bass in unison, an octave apart.
In Royal Blood, he can mute either line, so that the bass can kick back in, or the pseudo-guitar can solo.
This was pretty common, using Rick-O-Sound (the Rickenbacker 4001 originally had a resistor on the bridge pickup, that filtered out the low end - of course a lot of people snipped that resistor to have a full sound from that pickup), where you'd send the neck pickup to a bass amp, and the bridge pickup to a guitar amp - perhaps through effects etc.
Death From Above have been utilizing that technique from the get-go (though through 2 bass amps).
You could just as easily take the feed from the bridge pickup of a 4001, and put that through an octave up effect, prior to the guitar effects, and amp.
Combining Death From Above / Royal Blood technique bass, with GVSB / Ned's / C$C low end bass, would be absolutely awesome - but I've been trying to do that for decades, and never found the right combination of 2nd bassist & drummer...
The drummer is a truly major component in the success, or failure of a band like this.
It still boggles my mind that Ned's Atomic Dustbin were, on average, 17 years old when they put out that first record (the drumming on "Aim" really turned a lot of peoples heads, across many genres, at the time), and the girl who produced all their records, up to & including their debut album, was only 21 years old.
Older, and wiser, but a tremendous drummer none the less, Girls Against Boys sound is defined more by their drummer, than the fact that 50% of their songs feature 2 basses (check out "Tucked In", or "Kill The Sex Player").