Thank you for the advise and insight, Jason. You're very right about the luthier aspect, and another issue is that weather has been pretty extreme here for past two weeks as a arctic breeze from Siberia hit Finland. Two old and repaired cracks and one seam opened up as temperatures went down and air dried to extremes. The bass is a mess, and in the need of a new bridge too. Unfortunately, I'm running on fumes financially atm, and I have to wait a bit to get the bass checked out and worked healthy. Temperatures are going up now, and so I have my fingers crossed about the cracks not spreading more.
I take the advise of sticking with Spirocores to the heart, and will get into fine tuning the setup when the situation allows. Some stuff I can do on my own, bridge and nut shaping and string height / tailpiece lenght issues, but anything about soundpost placement or fingerboard shaping is way beyond my pay grade. I've thought about getting into soundpost zen, but will need the tools along with serious study on the issue, obviously. This would be a long run goal.
My needs from the bass are similar to yours in that way that arco has become more and more important, along with the musical reality beeing similar, I play mostly folk music and stuff that could loosely be described as americana. Most of my playing and even most of the gigs are fully acoustic, and so I need a bass and setup that is able to deliver, while still beeing manageable. I dont slap, but pizz and arco are about 50 / 50 in my musical reality.
However, when that Spiro w G string went back on, the bowability factor came up accordingly, no more wolfy woolly mess. As I wrote earlier on the thread, Spiros are The Arco String for me and my bass.