Why's there a need to? If it's highly unpleasant and there's a shortage of people willing to do it then surely it's a perfect opportunity for the development of self-cleaning tanks...
As it is most of the truly unpleasant jobs of previous centuries don't exist anymore - if someone had found a way to make gong farming pleasant (look it up!) then flushing toilets and town sewerage systems might never have been invented...
UBI would go a long way towards pulling the very poor up out of the cycle of "I'll take whichever bad choice is least bad right now because I'm desperate."
Re a very complex problem with "nobody should be in such a weak position".
It is only complex if avoiding questions about the value of human dignity, and the inability of laissez faire capitalism to deliver that, need to be avoided.
I think libertarian socialism does exactly that but in this case what's being argued for is JG (and UBI) which would help empower many, so we shouldn't be arguing against those things (not saying you are.)
There are entire YouTube channels dedicated to it. Septic sucking is a function of capital costs not labor costs.