Both Moto Guzzi and BMW have a sump pan on their opposed twin engines. (Moto Guzzi V-Twin and BMW Boxer Twin).

I am not familiar with the Guzzi - but with the BMW you can remove the heads, cylinders - then drop the oil pan, remove the pistons and cylinders, then remove the rods with the engine still in the frame.  Rebuilding the upper end on a BMW Boxer engine is pretty easy and was one of the reasons the bike was so popular for folks using them to commute or tour.

The oil pump however is located behind the flywheel and requires the transmission case, clutch and flywheel to be removed for access.  It is very reliable and doesn't wear out on a BMW.....it gets plenty of lubrication!!!!!!