Oofta
Legend
One person's "realism" is another person's head scratcher. See the thread on weapon weights as an example.I understand that, it was expounded to me over and over again when I first joined here. Some of the changes I wanted to make wouldn't have worked probably, as other pointed out nicely (thank you btw), but so far I have not seen most of my groups proposed changes breaking anything in the game or knocking it out of whack.
And what is a thorough understanding? When is that reached? People still debate some ways the rules are "meant" to work. A good part of it is up to interpretation by the DM and players. And if someone wants to make changes from the beginning, there is nothing wrong with it. If it doesn't work out, change it again or try RAW and see if the group is happy with that.
While simplifying D&D is nice, too much begins to suspend a reality aspect that many people (myself included) enjoy. Sure, I want fantasy, too, but I want something based realism as well. To each their own.
So for the suggestions you've made, I'd just caution on a couple of things. First, D&D isn't particularly realistic because there has to be a great deal of simplification for the game to work.
Second, be consistent. For example, if paper is cheap and there's a morning newspaper (or wanted posters, flyers handed out on the corner, etc) I'd really question strict literacy rules. That's really campaign specific, but I always thought it was odd when some campaigns have print/paper everywhere and only a few people can read. At the very least, I'd tie literacy to classes and backgrounds as mentioned.
Third, personally I don't think it's particularly realistic for a higher level fighter to be fumbling consistently. I had a DM long ago that did that ... it was annoying and one of the reasons I left the game. I take the view that a high level fighter may actually be feinting/parrying/swinging less often than a low level fighter. They're just more effective at it and have a better chance of landing a wounding blow.
Last, but not least, I'd still suggest running for a bit with standard rules even if it's just a one-off fight or ten so you and your group get a better feel for the game. It's your game and I know I have some minor tweaks, but I started with generic rules first.
Good luck, have fun, discuss rules changes with your group.