Hmmmm Personally I would stick with the Extra Object with Overlapping Detection..I use them for most of my checks...They function exactly like Raycasting in 3D..
What was the main issue with using a Faux Ray cast object..I think they work fine..
You would only need a single object in that example CapX...
And just check Overlap for each box and update your Variable to show the Object number that is between the two points
The only issue you would have there is if the Ray Cast object overlaps more than a single Block...But I am guessing that you would have the same issues with your Virtual line..
I tried the ray cast and it works fine...Not quite sure why you dont want to use them
Can you elaborate on your Problem?