Blow-by solution

[unfazed]

I would go the second engine route. It is easier to replace an engine than strip it down and hope it works.  As these bores are nikasil coated you would end up with the problem as before, therefore wasting money. In any case fitting new rings on an old barrel is never good practice due to "stepping" of the bores.
Taking out and putting the engine back in and is best with 2 people but can be done with one person. Just make sure you remove the front engine mounting bracket as the engine cannot be removed without removing it.