Agility and low weight already increases strafing speed (and acceleration) a lot.
Strafing abuse (usually just to get a faster s key) is already a problem in melee combat. About dodging projectiles I'd rather see projectile speed decreased (same effect without breaking melee) and about dodging cavalry it seems to me cav should be able to hit something. Horses already have the maniability of trucks, and have to go extremely slow to bump anything moving. Increasing human agility should go with a global horse maneuver buff.
#1 - Strafing would be increased across the board, resulting in a net null in regards to melee. Foot work is an important part of combat, just like real life combat. A boxer without footwork, no matter how powerful, will never be a world champion. Using the term "abuse" for a mechanic that everyone has may be a poor choice of words for you as it hints at a bias.
#2 - Decreasing missile speed is a terrible idea. There are already multiple issues associated with slow missile speed. I'm not going to list all of them.
#3 - Increased lance angle will allow
skilled cavalry to still hit their targets while removing the "free hit" from a horse bump from those who are unskilled and miss most of their weapon strikes. Unaware opponents will still be free kills.
#4 - Increase to turn rate will allow those with concrete boots to adjust to the dancing melee circling them.
#5 - to Kato and LordRich - Yes, it may have a huge impact on melee. It will allow an aware melee to avoid ranged missiles easier. It may add another dimension to melee vs melee, yes. I'm no melee myself, but as an objective outsider, you two sound like a couple strength lobbyists who are concerned that you won't be able to stand in place trading blows. You know how to break the attack/block/attack cycle? Make footwork important.