Initial Engine inspection

This is a tiny little engine (74cc) and as such not a problem to remove from the bike (especially as quite a few parts are missing from it :-(  The most obvious thing being a carburetor.
Its clearly had some abuse over the years - but I guess I shouldnt be surprised for a scooter of more than half a century old.  There are some damaged fins on the head, and the lug on the exhaust manifold has been cracked off

The gearbox (though technically its not a 'gear change box' - its more of a transmission box) appears to still be holding oil.  On the flywheel side we can see that the cowl and starter mechanism is missing

And the starter engagement ratchet gear is quite damaged - this is a strange double layered arrangement that is riveted on - is it original?

The variable belt transmission appears to be in ok condition.  Note;  When I made my 'winning' bid on ebay for this bike, I had no idea that it had this strange 'automatic', gearless and clutchless arrangement.
Im not sure if there should be a cover over this side of the engine - I havent yet seen a cover in any of the examples I've found on the internet

Madeningly, the variable belt lever (I have yet to work out how this works) has been snapped off

When I picked the bike up yesterday from the seller, we tried to turn the engine over - it wouldn't budge and so I assumed it was seized.  However, once on the bench and dripping in WD40, I found that the head and barrel lifted easily (in fact from what i could see the piston looked good - though i haven't fully removed the barrel yet).  One of the head/barrel studs is snapped.
It turns out that the jammed engine was due to corrosion between the flywheel and stator.

I need to do some more investigation into the state of the engine, but Im starting to wonder if it was once a "spares or repairs" donor vehicle - there is an awful lot missing (though on the up side there is still a fair amount left).  If the statement is true that the Manurhin Concorde was the 3rd most popular scooter after Vespa and Lambretta, there could be a chance that these missing parts could be replaced - and that lifts my spirits a little - Ive clearly got to get talking to the specialists and enthusiasts - and most probably in French or German.
I wondered also if I might even be able to fabricate some of these missing / damaged bits myself? Do I want to simply return the bike to the road, or do I want to return the bike to the road in as original a condition as possible?

I keep going hot and cold on this now.  One moment I like the challenge, the next I think its one step beyond hope.
I wonder if I could acquire a complete engine??