Unless I'm missing something really obvious why not just remove the radiator and/or the condenser?

You'd be looking right at the bolt and could utilize any of the standard bolt removal techniques, Ez-out, drill-out, weld a bolt onto the exiting bolt, ect. No need to destroy the water pump, clutch and buy a reciprocating saw. BTW using a reciprocating saw 1 inch from the radiator is a great way to pretty much guarantee you'll be removing the radiator anyways to replace it when your saw blade slips and nicks up a couple rows of highly fragile aluminum in the radiator.

It's been awhile since I've removed the radiator on an OM606 but as I recall it takes about 5 minutes.

__________________
98 Dodge-Cummins pickup (137K)
13 GLK250 (157k)
06 E320CDI (341K)
16 C300 (89K)
82 300GD Gelaendewagen (54K)