Keys are very capable of putting out extreme frequencies at extreme levels, yet pass through many PA systems with no issues, when dealt with correctly. A bass causes no 'special' issues for any PA that can handle keys.
In all the venues I've seen and done sound for, a pair of Xlr's from any instrument would be the dream scenario. Just plug 'em into the channel strips, correct for gain and balance in the mix and 'Bingo'..! I've yet to come across a PA that a bass could harm, if fed in this way. From the rest of your 'issues', I'd suggest that you were unlucky in getting a below-par sound guy, s'all. Change nothing.
We lent our 5-string Cort to Rodney Curtis (Maceo Parker bassist...) for our 3 Elephants festival, as his Lakland had a dead pre-amp. He changed the strings and played a splendid set with it (it sounded great through the Ampeg backline...). He signed the back (now worn off...), and was very happy with the way it played. At the time, that was our n° 1 bass. Happy daze.
In our little 'family' band, our Singer was the Drummer (and good at it...); I played bass. After a while Our Youngest picked up bass, so I switched back to drums (I'm a drummer...) and now our Singer is free to express himself fully as Singer/Frontman. He has no timing issues.
Latency is an inherent part of many instruments (most typically : wind...), and is dealt with, usually, by anticipating the 'beat'. Summoning a large gong is an extreme example; one does not just 'bang' it; it has to be prepared. Experience helps.
ADJECTIVE
Of, relating to, or produced by a prism, especially one which is transparent; (in extended use also) brightly coloured, brilliant.
Origin
Late 18th century. From prism + -ic. Compare earlier prismed, prismatic, prismatical.
There are many names I've only ever heard because of this Forum. OK, I'm a drummer, but I'd put the percentage at a rough 80% 'Who..?'. Not just because of old age; a lot of these famous folk are ony known to a limited circle.
And which causes few issues. However, this topic started with...
'... I'm feeling apprehensive about putting my hearing in the hands of sound engineers whose experience might not be that extensive. Something similar happened on our previous two gigs ...'
Taking back control removes the potential of having a repeat of those issues.