Is there a round feature?

I put this out to the modeling community, but thought I would share here as well.

How do you manufacturing guys get around this? Is there any Pro/Wire guys in this group?

We come across this issue every once in awhile in our Wire EDM Department. The wire needs a straight line radius because the wire should not bend.

Is there a round feature that will give us a point to point constant round between these two primitives.

A cone being intersected by a tapered cube. 

When we add a constant round the resulting (long) edges of the round become bent.

When looking from the top they look like this.

Here I created a boundary blend (yellow edges) between the upper cure and the lower cure (short edges of the round) to shot what result we are looking for. You can clearly see the bend in the long edges.

Is there a round feature that will give me the straight long edges of the round. Or, is this just impossible.

Thanks in advance for your help.

Dan