Patch Offset

You could create a custom fixture profile where the DMX output is offset by that 90 degrees, or whatever is appropriate in your situation. The other way is that you can bulk edit your presets/palettes for channel 2 pan +90 to add 90 degrees to your preset. You can grab all of your presets such as preset 1 thru 50 channel 1 pan + 90 and it will adjust them all by that amount. Of course you can run into an issue where you exceed the physical limits of the fixture and you don't really want +90 but rather minus 180 or something. 

Beyond those, there are two, what are probably better solutions:
1) Go through the trouble of properly hanging the fixture.
2) Use Augmented 3d and store your focus positions as XYZ instead of pan/tilt -- this is probably the best option, because now you can just adjust the fixture in patch with it's actual orientation and the console will do the math to correct the actual pan/tilt value. 

I get that, but I would use this more in the scenarios where I have 50+ focus pallets that all need to be updated the same amount. I would imagine it would handle limmits the same way relitive effects do when it hits a physical end of movement, it stops physycaly but continues virtualy. It's not very often I find myself needing evey last degree of pan and in many scenarios the offset would never put me in danger of hitting a physical limmit. Many other console manufactures have successfully deployed this feature and I would love to see it on the eos platform.

The problem is, that the Fixture can not move the hole 270° in both directions.
So setting a 0 point is false.

Rather use a Self defined Home Preset for the fixtures you like to correct.