If I just wanted to represent some of the possible effects of "Weapon Speed" without rewriting every weapon in the game, I might just apply the OCV penalties from Unequal Reach (FHC 173) to the Character's Initiative as well. That way a character with a longer weapon has a slight initiative advantage against an opponent with a shorter reach until said opponent made it past the character's guard.
However, conditional changes to initiative are a pain in the assets to keep track of. So I wouldn't bother with such a house rule at all personally. Likewise I usually discourage Character's from having highly conditional forms of Lightning Reflexes as well.
HERO does not have default solutions for guarding a door, for example, or preventing someone running past you. It would be quite easy to build a lot of these things as powers, low end available as Everyman and points spent to make them more reliable.
If I am hunkering down, defending and holding my ground, I should be able to reliably hold things up long enough for my friends to escape.
There actually is a rule for guarding an area, see FHC 183. Basically you hold an attack to attack when someone enters your immediate area, and the target suffers 1/2 DCV unless they entered the area specifically to attack you.
If you have something like Legsweep or Martial Throw, Guarding An Area could be used to prevent passage fairly effectively, and if you don't you can still attempt a Grab or Trip maneuver against them.