For my homebrew i use a reduced set of attack tables: 1 for melee, 1 for ranged, 1 for sweeps/grapple, 1 for unarmed strikes and 1 for natural attacks. To differentiate weapons I apply a modifier based on the weapon and it's size, it works well and is easy to make it fit a normal size GM screen, so it speeds up combat a lot.
I used RMU table as start point and after adjustments I get results that are not too much different from the original tables. However to make the table for weapon adjustments I made a classification of the armor type in four groups, in a similar way that MERP used to do: No armor, Light armor, Medium armor, Heavy armor. In this way a weapon may be +5 vs no armor, 0 vs light and medium and -5 against heavy. I'm overall satisfied of the result, but I'm not entirely sure fo the armor classification. I divided AT in this way:
No armor: AT1
Light armor: AT2, AT3, AT4, AT5, AT6
Medium armor: AT7, AT8
Heavy armor: AT9, AT10
But i'm not really sure of AT6 and AT9, though this way seems the more correct from a mathemathical point of view.
Any advice? Should AT6 or AT9 be moved to medium?