Further Low Fantasy musings

In my "D&D as low fantasy" post, I discussed how I would house-rule 3.5, the version that I'm most familiar with, to be something that I could play. The more I think about it, though, the more I think that Pathfinder 1e would be a better baseline to play with than 3.5. It's basically the same game already, but a bit streamlined in some respects, and with more options. A little bit more powerful, but I'm adding steps below that mitigate that. And frankly, I like a flatter curve rather than zero to hero anyway. I absolutely want to limit the soaring heights of hero, but let's also not start literally at zero. 0-level character funnels and stuff like that is fun as a gimmick, but not what I want for a long-term, serious campaign. Let me reiterate and expand just a bit on how to do this. I'd still like to do this, honestly, and will probably make this an official page at some point; how exactly to use these rules to get the low fantasy that I want.

• The number one rule is: don't play with powergamers! Late in 3.5's life cycle and throughout Pathfinder 1e, it certainly had a reputation as a powergamers' paradise, with all kinds of optimization combos and stuff that you could use. If you instead look at all of these options from a roleplayers' perspective, as offering you all kinds of ways to customize your character experience rather than ways to optimize your mechanical character experience, most of the problems with the game go away on their own. That said, maybe something like "The Elephant in the Room" help to mitigate it. 
• Use E6. If it works for 3.5, it works just as well for Pathfinder 1e, since the games differ only in details, not at all in base structure. 
• All races beyond core need to be explicitly approved. I'll try to make a lot of stuff work, but a lot of stuff simply won't, no matter what. Especially the animal people.
• All PCs are by default, banned from taking a full spellcasting (or psionic powers using) class at 1st level. You can multiclass into it at 2nd level without penalty, however. "Half-casters" like ranger or paladin, etc. can still be used as is. And non-casters can, of course, also be used as is right away.
• Incantations were never officially introduced, I don't think, into Pathfinder 1e, but they were certainly present in d20 D&D and Rituals work almost exactly the same way in 5e. Higher level spells that you want to be present in the game can be converted by GMs into Incantations or Rituals, but that, of course, makes them unlikely to be useful in combat, because the casting time is in minutes or even longer rather than in rounds.
• One of the main reasons I was reluctant to use Pathfinder 1e vs 3.5 is because I wanted psionics from 3.5 to be available. For this reason, I include Dreamscarred Press's Ultimate Psionics as a "core" book useable in the Pathfinder version. I know, I know—it's not exactly just a direct port of the 3.5 psionics into Pathfinder. It couldn't be even if it wanted to; the Expanded Psionics Handbook material was added into the SRD, but the Complete Psionic material was not. While I miss the Lurk or the Ardent sometimes, they did a pretty good job of attempting to get the same material, more or less, out of their book. It'll do. Psionic classes, like spell-casting classes, however, are subject to the same "half-caster" rule at first level, i.e., full-casters can't be taken at 1st level. You'll have to use your best interpretation of what is considered a "fullcaster" psionic class, but certainly the Psion and the Wilder qualify, at least. I don't remember the Pathfinder specific rules well enough to comment otherwise; I know for sure that the soulknife and aegis, for instance, probably don't. Anyway, maybe this is a moot point. I don't know a lot of psionic players, and if there are psionic players, they often tend to gravitate to the soulknife for obvious reasons; because it's like a combination of Psylocke from the X-men and a Jedi or Sith. It may actually be the only psionic class that I've seen played, come to think of it, and I know that I've been in campaigns with at least two of them before.
• If needed, and if you play into the E6 feat progression part of the game, higher level class abilities can be converted into feat chains that characters can continue to take after they hit the max level cap of E6. Yeah, this will require a little bit of review and work, but it's not a big deal. And you have to run quite a long campaign for it to even be relevant anyway. Speaking of which, I'll almost certainly ditch XP and do something like 5e's milestone experience. Which will be a fair bit slower as well. There's no rush to get new abilities. Get used to the ones you have for a while before you start immediately adding new ones.
• Because of the class list and archetypes formula of Pathfinder 1e, which built on the same idea in the Complete books (and others) of 3.5 as well as the PHB2 but greatly expanded and in the game almost from the get-go, I don't think prestige classes are nearly as important in Pathfinder 1e as they were in 3.5. I'm almost tempted to just say ignore them completely. However, if as GM you want to allow them, you'll have to look at them carefully; if you think that they're OK, they should be playable at 2nd level. Let the PC take as many of the prerequisites as he can at 1st level, and then just waive the rest of the prerequisites and let him take 5 levels of the prestige class, as if it were a fullcaster class. Feel free to veto any prestige class, or even the entire concept of them. Pathfinder with all classes and archetypes enabled is already even more open of a game in terms of optional character concepts than 3.5 was. Because it was built on the 3.5 chassis after seeing what 3.5 did, and it deliberately enabled some of the better late appearing ideas early on.
• Sanity rules aren't necessarily necessary for low fantasy, but I like them. There's lots of options out there, but if I'm doing Pathfinder 1e anyway, why not use the Fear and Sanity and possibly even Corruption systems from Horror Adventures? I'm not as much a fan of Corruption as a mechanic, but it could be useful in the right game. Fear and Sanity I always like, however.

Now, don't get me wrong. I'd still prefer to use my own rules-lite, kinda sorta old school adjacent system. I like rules-lite kinda sorta old school adjacent systems as long as I'm not playing in the OSR playstyle; I'm very much in the trad camp, and I've always been interested in D&D because I liked fantasy fiction and roleplaying, not because I was interested in any of the gamist elements of D&D, or the dungeon-crawling environment, or anything like that. But, I have a lot of nostalgia for d20 games, and this is something that I could run with and enjoy. And I do enjoy using the 3.5 and Pathfinder 1e mechanics of character building, not for the optimization nonsense, but for the built-in customization for roleplaying that it offers.