Just a thought I would like to share. I'm not expecting this to be anything grand or the like, but kinda like an optional rule. Might make the game last a bit longer though, so some people might not enjoy that.
When fighting in the Assault Phase, if two or more models are fighting each other in the same Initiative then after the To Hit rolls are made, the player(s) can choose to cancel out a enemy successful To Hit roll(s) by sacrificing your own successful To Hit roll(s) of equal worth, so that it's like blocking. If any To Hit rolls of 1 or 2 happen they still miss and cannot be used for Blocking purposes either. Any player can choose to "Block" regardless of turn. Also, lower Initiative models cannot "Block" against higher Initiative models.
///Example: Space Marine Sergeant is fighting two Chaos Marines in close combat. The Sergeant rolls 4 and 5 on the To Hit rolls. The Chaos Marines rolls 4 and 4 on the To Hit rolls. The Chaos Player decides to "Block" the Sergeant's To Hit roll of 4 with his own To Hit roll of 4. (Narrative-wise, a Chaos Space Marine blocked a blow from the Sergeant's Chainsword with his Bolter before his head was decapitated.) So now all that remains for the To Hit rolls is the Sergeant's roll of 5 and the Chaos Marine's roll of 4.
At this point, the Chaos Player wants to "Block" the Sergeant's To Hit roll of 5 but cannot, as the Chaos Player did not roll a 5 or higher. So the Sergeant's roll goes through and follows the regular process of the To Wound roll and such. (Narrative-wise, the Sergeant's first blow was blocked by the Chaos Marine's Bolter, but before the Chaos Marine could recover from the blow the Sergeant struck more skillfully and eviscerated the Chaos Marine's neck.)///
If the two or more models fighting each other possess the same Initiative but not the same Weapon Skill, then use these modifiers if you wish to Block.
///Example: Guardsman Deadmanwalking is fighting Ork Nob Gutrippasmashysmash in close combat. The Guardsman rolls a To Hit roll of 4 while the Ork Nob rolls To Hit rolls of 4, 1, and 2, resulting in one hit and two misses for the Nob. While ordinarily the Guardsman can choose to block with his To Hit roll of 4 against the Ork Nob's To Hit roll of 4, the Nob's Weapon Skill is one point higher then the Guardsman's Weapon Skill so using the chart above, the Guardsman needs a To Hit roll of 5 or more to "Block" the Ork Nob's attack. (Narrative-wise, the Guardsman raises his lasgun to block the Ork Nob's Choppa, but the Ork Nob's attack is so ferocious that even though the Guardsman tried to block the attack the Nob just batted aside the lasgun away, almost knocking the weapon away from the Guardsman) The Guardsman fails to "Block" and the rest of the fight carries on as normal, both Guardsman and Nob roll their To Would rolls and such.
Meanwhile, on the other side of the galaxy, a Tau Fire Warrior is fighting a Ork Boy in close combat. The Fire Warrior hits the Ork Boy with a To Hit roll of a 5 while the Ork Boy hits back with To Hit rolls of 3 and 2. The Ork Player decides to "Block" the Tau Fire Warrior's To Hit roll with his 3 since the Ork Boy's Weapon Skill is two points higher then the Fire Warrior's Weapon Skill. While with the modifiers will decrease the "Block" To Hit roll of a 2, a roll of a 1 or a 2 is still a miss in close combat and thus cannot be used to "Block."///
If a player wishes to, they can hold on to any amount of To Hit rolls they made and use them to "Block" against attacks from lower Initiative foes. However, if the player wishes to hold onto these rolls then they cannot use those rolls to attack.
///Example: Chaos Aspiring Champion is fighting a Black Templar Initiate with a Power Axe. The Aspiring Champion rolls a 5 and a . As the Initiate does not roll To Hit rolls yet, the Aspiring Champion can decide if he wants to press his attack with his rolls or to keep the them to defend against the Power Axe threat. (Narrative-wise, the Aspiring Champion is bracing himself by taking a more defensive stance, waiting for an opening to take advantage of to slay his opponent.) The Aspiring Champion decides to hold onto the rolls and hopes that the Initiate doesn't roll higher then what he has. The Initiate rolls To Hit rolls of 5 and 3. The To Hit roll of 3 misses while the To Hit roll of 5 hits. Thankfully, the Aspiring Champion was prepared for this situation and uses his kept dice earlier and "Blocks" the To Hit roll of 5 with his own. However, the To Hit roll of 4 the Aspiring Champion had kept is wasted and is gone after the phase is done.///