so, I just had this thought, what if the modifier for defender has defended against previous attack was increased to -2 instead of -1. What would be the effects and would you see it work?
a few thoughts:

-more deadly. obviously. For both sides.
-faster combats, due to more deadly?
-more full defense actions.
-even longer combats, due to more full defense?
-more realistic combat situations, that last longer than 1 combat turn, due to (N)PCs using full defense and cover more often
-better chance to actually hurt high spirits with ItNW

This only really becomes more deadly if larger numbers happen, which is something squarely in the GMs toolbox. 10 gangers would pack an unseemly punch after all that bonus. I could see this working if other factors work to balance it. Like a 500 point game. Otherwise, this is heavily weighted to make "rapid dominance" combat actions against larger groups useless.

One side-effect of longer-lasting combat is that the ridiculous response times of LS and KE could be brought back in line with "reality". But I'm not sure that makes up for the fact that...well, combat is now longer-lasting in the first place.

I do like the imagery of "piling on" in an effort to hurt something like a spirit

Not by much. Only if the modifiere reduces the defense pool to 0 and removes one roll.
Either that or shorter combats due to hitting harder more quickly (more FA, bigger guns, more emphasis on surprise and coordinated action etc.)
Full defense and (full) cover is not combat, that is hiding.
A bit yes, do to more net hits.

Mabye a way to do it a little different, taking a page from Conan (hey...I liked the game )

Not only does someone get the -1 per additional attacker, attackers get +1 per previous attack in the same way.

Just reading that it sounds like I am not doing a very good job explaining.

example: Bob, Chuck and Fluffy are attacking Jim.
Bob attacks Jim (No mods)
Chuck attacks Jim (+1 die for Chuck, -1 die for Jim)
Fluffy attacks Jim (+2 dice for Fluffy, -2 dice for Jim)

or
Bob attacks Jim (No mods)
Chuck attacks Jim (+1 die for Chuck, -1 die for Jim)
Jim attacks Chuck (No mods)
Fluffy attacks Jim (No mods)

If you were to go that route, i'd make them independent. Defense penalty is -1 to defender. +1 dice to attacks is on a per attacker basis.. so...



example: Bob, Chuck and Fluffy are attacking Jim.
Bob attacks Jim (No mods)
Chuck attacks Jim (no attack bonus for chuck, -1 die for Jim)
Fluffy attacks Jim (no attack bonus for fluffy, -2 dice for Jim)
Bob attacks Jim again (+1 die for Bob, -3 dice for Jim)

Sounds like Friends in Melee to me... Already have a rule for that.

not really...at all... unless you quoted me on mistake instead of Vykos.

what i suggested adding completely ignores whether other people are attacking or not.
If Bob attacks Jim after 20 of his friends fire also fire at Jim, Bob still gets no DP bonus.
The -1 penalty to defense test is already in the rules.