Mega Dave pretty much covered it. And even more so if you are sending to a frickin guitarist to mix in. Don't send it to him with your ultimate bass tone because it will change...for sure. Send him something he is bound to change into your tone. In other words, don't send something that will require a huge click adjustment because you're fucking with the guitar picking, and don't send in something that woofs out and gets muddied up under the drums. Like was said, find that sweet spot. But unfortunately for you, you must find it before you know where to look. Flat as you can stand it is in my opinion the best way to go. Maybe a little mid boost on the bass knobs.
But after saying all that, on the other hand, don't be afraid do dial in something good and sounds killer all on it's own. Saying flat means that you must already have a naturally good sounding bass. It must sound like a bass, and not sound like a bass that's all eq'ed out. Fender Precisions get the most accepted by nonbassists when they are recorded directly into the console, flat. But you probably have a better bass than a Fender Precision. So just remember to play clean and only focus on boosting the common frequencies(100, 200, 500, 1000 HZ), that might help not getting lost after trading hands.
Also, fix your inconsistencies in your playing by touch. Lean back in the softer parts and dig in for the faster shit. Play your improvised parts dead on and smooth as hell. Be your own compressor, naturally. Then when "Mr.Oh no, what is that clicking, rattling and clacking??" gets a hold of your naked track, they won't have to compress it to nano levels. That's usually the problem of getting that muffled and overdriven sound, which always leads to getting lost in the mix.
Man, it's really hard to throw advice out in a few paragraphs that has, and still is, taken over 20 years for me of fighting to get things the way I like to hear them. The way it should be. It's an experience thing, and it's a trial and error thing man.
Fucking good luck...and Namaste man!
SDG