The designer really should not have to worry about kerf comp. This is the vendors responsibility. A net size and shape DXF should be all that's required on your part.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

This comes right down to the machine operator.
Supply a drawing of what you want, and let the operator figure out how to get there.
B.E.

You are judged not by what you know, but by what you can do.

Here’s the part I just had waterjet cut. This company said they cut to net shape from the dxf file and that is exactly what they did. The measurements are dead on for our requirements. The cut surfaces on this part are “medium smooth, Q3”. That is perfect for our production, but on some parts that we will sand and polish, I will add a little of my own offset where I want it.
For info, this is one inch aluminum 6061 T651 plate. There was no significant (for our purpose) taper in the cuts. I had four of these cut at a cost of a little over US$250 each. It would have been over 300 for a steel fabrication ($fit up and welding$). It’s to carry some suspension bits for a car. A member of the team wants to offer plans to build the car and include all the dxf files needed for the parts with the drawings.

• http://files.engineering.com/getfile.aspx?folder=9f65c924-2478-440f-9dca-b7

If you know you are going to sand/file polish then give the guy a DXF with the hole undersized by the amount you want to remove. If you start asking for offsets, number one it will put the price up number two , he may offset to the wrong side of the line. Ask me how I know about that.
B.E.

You are judged not by what you know, but by what you can do.