I am normally a huge fan and advokate of realism, but you have to admit, that this game (cRPG) is not meant for simulating that. I had to learn that too everytime I brought this up.
If you want semi-realism, it would be easier to go and try "Vikingr" or "1257 a.d.". Both of these mods take a very good step towards realism, and Vikingr is even multiplayer and quite fun.
Because, in fact, swords were weapons for rich people (a lot of metal, a lot of production time, very very expensive, even the simpler versions), not common for the common man, and longswords even less. They were sidearm for cav (because of length, and because you can use it as a lever and wedge with both hands against plate-wearing folks.
Armor penetration is of course not that easy, but I personally believe it wasn't always necessary, because most people back then couldn't afford more than a gambeson or something similar. And even that was worth a fortune.
Now, what we COULD do in cRPG, is getting the prices up like crazy for everything with more metal than a spear and nerfing every speed value to a low standard. Then, when even having a sword and a chainmail or something is considered wealth, you can start talking about cutting/not cutting and penetration physics, imho.
But this won't happen in cRPG. Maybe in M:BG, I am hoping.
Until now, my apporach for speed calculation would have been: converting the damage values to something that displays sharpness, and the speed and weight/length values to something indirectionally proportional to each other, the longer and heavier it gets, the longer you end up swinging it. maybe: swingtime = 1 / someValue * weight * (length/10) // with someValue being <1 as a global standard
BUT I really don't know that much about physics, AND I don't know how the game does it now. So this is just a sketch. Food for thought hopefully.