(Almost) complete renovation of a single-family house from 1968 / what costs will we face?

I am sure that for you it paid off or it would have been impossible or more expensive otherwise, but cost planning should not necessarily be based on such special cases.

I am actually not a special case. Buildings from the 60s often do not have a suitable eaves overhang for an ETICS.
That is why I specifically asked the OP about it and already pointed out in my post that I chose the insulation differently because of the missing roof overhang.
Please always read my posts completely. I just don't want the OP to think: "EPS insulation is cheap. Let's do it." And then it doesn’t fit and (significant) additional costs arise. Or new windows cannot be installed from the outside ==> suddenly expensive work on the window reveals is necessary. Tens of thousands of euros add up very quickly during a (core) renovation.

From my professional experience, you are looking at around +/- €150/sqm all in for existing buildings (not new construction). And then it depends on what extras come: reveals, connections, plinths, etc.
If it is as elaborate as mine, you end up at €220/sqm. Then another €80/sqm surcharge for higher-quality insulation and suddenly there is a three at the front.

I am actually not a special case. Buildings from the 60s often do not have a suitable gable overhang for an ETICS. That is why I explicitly asked the OP about it and already pointed out in my post that I chose the insulation differently because of the missing roof overhang. Please always read my posts completely. I just don’t want the OP to think: “EPS insulation is cheap. Let’s do it.” And then it doesn’t fit and (significant) additional costs arise. Or new windows cannot be installed on the outside ==> then expensive work on the window reveals is necessary. The tens of thousands of euros add up very quickly in a (major) renovation.

You are absolutely right, and these are exactly the issues for which we wanted to turn to the forum. We know that with such a big project there can always be some five-figure surprise waiting for us – but it would be nice to consider as much as possible in advance. The expert also addressed the fortunately large overhang directly during the inspection, so we are indeed lucky.

Your approach can definitely work.
We did it exactly the same way.

:D So it is possible!

Perhaps now is the right time for it, there aren't many buyers around. A year ago it probably wouldn't have worked...

You can tell that times are currently changing... The house would probably have been sold two years ago in a bidding process starting at 800,000€.

That is already very expensive – I won’t take my project, as we really got very cheap exterior insulation & plaster, but as a random example from another project carried out in early 2023: approx. 340 sqm to be worked on, for everything (fixtures, base rails, ETICS EPS 032 boards, corner protection, sealing tapes, reinforcement, lightweight plaster, primer & topcoat) it ultimately cost about €45,000 gross, or about €132 / sqm all-inclusive (except scaffolding, as it was calculated/contracted separately).

That sounds like our rough estimate is not too far from reality (plus/minus €10,000?!), provided no nasty surprises await us. Scaffolding, of course, can still add quite a bit to the cost.