So here is the set of customized parameters I use (and now it's giving good results!)
Wall Line Count: 3
Optimize Wall Printing Order (so that the 3 circles outlines are done all at once on the same circle before going to another circle)
Top/Bottom thickness / layers: 0.00mm, 0 (Gero's tip to permit "Infill before walls" option to apply from the first layer: thanks a lot!)
Infill density: 100% (for parts like empty cases / mounting plates this is usually fine)
(Infill before walls should already be checked)
Enable Retraction (permits to avoid leaking too much material on travels between things to print)
(Retraction extra prime amount : 0 mm³ is fine with PLA on my printer but in case of leakage, you may try to put something here so that enough material is pushed on arrival to compensate the leak)
Combing mode : Off (so that most travels are done using straight line + retraction, so it prevents unnecessary material leakage during travel - but if there is some, it's more visible).
This still makes first layer usual tuning important but at least, tiny holes on the 1st layer aren't a nightmare anymore. As usual, fine bed leveling (for those who are lucky enough to have a really flat bed), glue stick or spray, thick first layer (so that missing material length on arrival is as short as possible) and Initial Layer Flow > 100% if necessary (slightly pincushion shaped bed) are my usual hacks to work around the many imperfections of the process and this printer.
Unfortunately, for parts on which 100% infill density isn't an option, setting Top/Bottom thickness / layers to 0 may not be possible, causing small holes circle to be printed isolated on the plate before their surrounding.
In this case: The combination of "Optimize Wall Printing Order" with 3 outlines wall, Enabling Retraction and Combing mode OFF may reduce the failure rate despite this problematic print order