The Stage Bug works perfectly with passive instruments, unless they have a particularly low output.
Even then, we all have such extreme levels of overkill built into our rigs these days that you're never going to run out of headroom.
Sending to lines independently can easily lead to problems with monitoring, unless you've done a fair bit of prep work beforehand.
If you're running your bass through backline (with a DI to the PA) so that your bass rig supplies the monitoring you need, then running your synthbass through the same backline gets rid of that (potential) problem.
Yup, unless it's a 4/4 or has an unusually deep body for some reason.
If you were closer, then I'd happily flog you mine at a big discount (after testing, natch).
Maybe find another Basschatter up East Anglia way who has one and will let you try it?
https://www.gak.co.uk/en/hercules-ds590b-double-bass-stand/53065?gclsrc=aw.ds&&gclid=CjwKCAiA2L-dBhACEiwAu8Q9YKPCYFwLrMhaZRolmuh5gD5-SL4av8vcA3bYuAnV214oDuBgsUDEiRoCBrsQAvD_BwE
Whereabouts in the UK are you?
I've used one of these for years.
https://www.thomann.de/gb/km_stehhilfe_14045.htm
Built like a tank, easily adjustable and very comfortable, especially if you get the optional backrest.
Best set list software I ever found was an obscure product by a software house you'll never have heard of.
I think it was called 'Excel' or something equally silly.
Best thing is when you turn up at a jam with a bass that looks like you found it in a skip, and when all the guys with their Stingrays and Dingwalls and Sadowskys have been up and played root+5 for their three songs, you provide 10 minutes of aural chocolate ...
Different world now, with crowd-sourcing and loads of freebies on that there Internet thingy.
If soundmondo didn't exist then the Reface DX would be an awkward beast supplied with a wide range of fairly useless sounds as standard. A couple of hours on soundmondo and I have every sound I am ever likely to need (playing in general covers bands and a specialist soul band) and all with no need at all to learn how to 'tweak' any parameters, still less actually program anything.
Just slave it to a 76/88-key unit with the (supplied) midi break-out cable. That's what I do with my Reface CP.
I hate midi and don't even begin to understand it (AFAIK those are 5-pin DIN plugs) but even I could manage that much. 🙄