A few thoughts of mine, if i may.
I understand and approve the idea of TFC combat focusing more on PvE than PvP. Obviously people are fighting against the nature more often than with each other, even on PvP encouraging servers. Therefore adding new interesting mobs, features like boars charging into players etc. should definitely be prioritized, no doubt.
As of the idea of using different arrows - flammable, metal, stone - and different bows, I thought that making arrows work like javelins do right now (make them stack obviously, be subject to current arrow physics still, having various damage depending on arrow type) and having a check running for a bow (just as how using a chisel needs a hammer on the toolbar) would probably save some problems with coding, and add an easy possibility of choosing which arrow you are about to use. Changing the currently used bow on the toolbar would of course alter damage/reload speed/range according to the bow type used. How to make different bows is yet to be decided, as I am no expert, but I assume the vanilla bow would be easiest to make as it is now, and more advanced ones (like composite bows/longbows) requiring some advanced crafting methods. I also like the mentioned before arrow reclaiming idea, which may work like the javelins have a chance to be reclaimed after hit.
I would love to see implemented the removal of the silly push-back-on-being-hit thing currently in place, except for really heavy-impact weapons like hammers, maybe maces, and strong mobs like bears or boars. You do not fly away when hit by an arrow, like previous persons stated.
Crossbows would be a nice addition. They were known in history even in Roman times, with the weapons being used in China as well, not making it such a rare occurence, therefore they can find a place in the TFC technological level. I assume an easy way to code them would be by making them load for a fairly long time compared to bows, with the starting damage of string pull extremely low and fully loaded damage well above any of the bows present. You would have to stand completely still to load them, too. That would prevent their abuse in combat and add some balance. For simplicity's sake, make crossbows and bows use the same ammo.
The light/medium/heavy armor speed penalty is absolutely essential, so that running around in heavy plate is not a daily habit of a player once you craft one, but instead you use it when you have to. It is tiring to wear heavy armor, and I do not recall knights sleeping, eating and socializing with heavy armor on in everyday life just because they owned a set of that, so the player shouldn't wear it either while farming or fishing because of the movement speed penalty, and possibly a hunger increase. You want to stay quick while doing mundane tasks, for efficiency's sake, so you could trade off some protection for speed, choosing medium or light armor over that heavy plate you've made.
Another idea connecting to the mentioned above is an armor stand item, allowing you to store your armors when not in use. With no possibility of putting one in a chest simply as it is too large to fit, that would be the best option, however I do understand that it does require much coding. At this moment that is not such a big problem, as you always tend to wear your highest tier armor available, but with bonuses and penalties of armor in place that will be more important to store what you are not using right now.
And my last thought, weapons should be indeed categorized into blunt/slashed/pierced damage. Heavy mail can be fairly easily surpassed by pierced and blunt weapons (especially crossbow bolts). What I thought would be good is to set maces to have a low, but fixed amount of damage that is ignoring armor (or being lowered by a very slow amount). Slashing and piercing weapons would inflict bleeding debuffs on targets, with the unfortunate victim losing health over time. Piercing wounds cause smaller bleeding, but have a higher armor penentration rate than slashing attacks quite sufficiently being blocked by armor. However, lightly armored targets would suffer more from slashing attacks, with stronger bleeding effects in place. Concussions by being hit in the head with something heavy would also be welcome, however I think that would be quite hard to code.
I hope that my post was comprehensible and helpful, I love this mod and I want it to improve. I know that those ideas may have engine limitations, are hard to code, etc, but I hope something similar may be impemented over time. Good job with everything done so far, devs!