Wrestling and grappling is often a confusing mess in RPG or introduces combat resolution which strays far afield of standard combat resolution. So I couldn't help but work this system up as a possible wrestling resolution method. It's inspired by some versions of subdual damage and is currently untested.
I'm going to introduce one new form of "damage" for this variant: Binding.
Binding is a damage score that accumulates against a target, when the total binding score of a target exceeds their STR score they are pinned.
Players and DM's keep track of binding as it accumulates.
The initial attack in wrestling is grabbing your foe. This is a normal attack roll that inflicts no damage and if successful at the end of the round a wrestling roll is made.
Grabbing An Armed Foe
Trying to grab an armed foe is dangerous. A fighter or Monster is allowed a free counter attack per level/HD. If this counter attack is successful the grab attack fails.
A combatant must announce the counter attack against any foe trying to grab them prior to the grab attack roll.
At the end of a round when two or more combatants are grappling each may make a wrestling attack. This is a standard attack roll except each wrestler also applies their STR modifier as an AC bonus when wrestling.
(some DM's may wish to pre-calculate a WAC for combatants).
If a wrestler makes a hit on a foe they inflict binding on their foe. Binding damage varies by size
tiny..........1d6-3 (can be 0)
small.......1d4-1 (can be 0)
The first successful wrestling attack establishes a hold. Foes may not move if they are held by one of the same size or larger.
Normal damage bonuses are added to binding damage.
If binding exceeds ones STR score they are pinned.
If no binding damage is inflicted in a round the hold is broken and neither foe is wrestling. Both have any accumulated binding damage halved and it will vanish at the end of the next round if no further grabs are made.
A pinned combatant may make no attacks during normal combat and is -5 in any further wrestling
An opposing wrestler inflicts 1d3 damage per following round if they wish to harm a foe with following wrestle attacks, Otherwise they may simply hold the pinned foe in place. One need not make a wrestling roll to hold a pinned foe but a foe may break free.
Breaking a Hold
If one foe hits during wrestling and the other misses the one that hits may choose to break the hold instead of continuing to wrestle. Both foes will have their binding damage halved and the binding damage will disappear if neither is grabbed during the following round.
Instead of applying Binding damage against a foe one can decrease binding damage against themselves on a successful wrestling roll. If binding damage is reduced to 0 or less opposing grapples are shaken off.
A foe who has gotten a pin on a foe may chose to throw them down or away. This requires a successful wrestling attack. In either case the victim suffers 1d4 actual damage and may hurl the foe up to 10' away, the victim is prone and their binding score is halved and will vanish if no follow-up attack is made next round.
Attack a Pinned Foe
Attacks against a pinned foe are made at +4 to hit. This includes opposing wrestlers.
Attacks Against Wrestlers
Others outside a clinch may attempt a standard attack an un-pinned wrestler. Such an attack is made at -4 and if a miss is made there is an equal chance of any random target being struck instead (with total miss being counted as an additional target).
Joining in a Clinch
One may choose to wrestle a foe an ally is wrestling. The grab attack to wrestle someone an ally is wrestling is made at +2.
Using Weapons While Wrestling
Traditional weapons may be used while wrestling during the standard combat phase of a round. Natural weapons & Small weapons are -2 to hit but do normal damage. Weapons much larger than a dagger are -4 to hit and do but 1/2 damage.
Most characters may not make punching attacks while wrestling.
Quickie STR scores for wrestling.
tiny- 2d6 (gnomes and bats)
small- 2d8 (dogs and halflings)
medium-3d6+HD (orcs and men)
Large- 4d6+HD (horses and gnolls)
Huge or larger 4d6+ twice HD. (dragons and giants)
the quickie sTr roll is to determine how much bindign damage ti takes to overwhelm a foe it is not used for other damage calculations.
Wrestling Really Large Foes
If one scores a pin on a really large foe they have either tripped the foe automatically throwing them down or they have clung on in such a manner the larger creature may not make an attack on the foe clinging to them. When clinging to a large foe one may make weapon attacks during standard combat but suffers the usual penalties to attacks when doing so. Once one has made the decision to cling they may not decide to change it to a trip on the next round but others may join in and trip the large foe.
Spell Casting and Psionics while wrestling
Spells may not be cast while wrestling. Magical devices may not be readied while wrestling. Psionics have a 50% chance of failing during a round of wrestling. At will powers of creatures may still but any requiring a hit roll suffer a penalty to hit, attacks that allow the defender a save allow the defender a +4 save bonus.
Wrestling creatures with touch attacks
Grappling a foe able to make touch attacks is foolhardy as the opponent will be able to inflict the touch attack in normal combat and during wrestling.
Grappling non-corporeal foes
One may not grapple a phantom or other immaterial foe.
Some non-corporeal creatures can hold or animate items. Items may be wrestled from their grasp as if they were small creatures.
More fun with Binding Damage
A DM could introduce spells or monsters that are able to inflict Binding damage. Some trapping/hindering spells could be rewritten to inflict binding damage over other more complicated descriptions.
Binding attacks with weapon such as bolas, lassos, nets and catch-poles could also be added to a campaign.