Ah! I have a Warco WM240 which came with the same problem! I simply took 'potential' aim for the the oiling point, using my oilcan spout, and drilled a hole in the casing. The size of hole was based upon some blind grommets that I already had (available from outlets such as Maplin) and, obviously, big enough to allow the passage of the oilcan spout. I merely have to pick the grommet out, with my thumb nail, and replace it after maintenance, leaving a neat and tidy finish when done. I do agree with your feelings, however, that this is an example of a lack of good design!
Trev T