the biggest problem with integrating variants into second and third generation Omnimechs (in terms of appearance in TRO's not canon) is that they do not share the same basic arcitechture that the original 3050 Omni's do. while in many cases I believe it can be fudged (particularly with the 3055 Wolf Omnis or the upcoming Woodsman) some designs are too far gone from the 3050 norm to integrate them into the current line of Omnimech parts.
in the case of the Cougar, the if you can figure out how to get it to accommodate Twin LRM 10s, twin LRM 20s, and Twin SRM 4s, all mounted in side torsos then all the other weapons are in the arms, and a resculpt MIGHT be made to accommodate Light Omni Arm parts in the mold of an Uller/Adder