The question here is not about the game, but about the metagame. I mean the characters will use gallons, inches, ..., but as game master is me who needs to tell them for instance how much time they take to reach their destination while traveling and it's me who needs to rule if they can conceal an item, for instance. And it is difficult for me to make it by using the imperial system. This is difficult to everyone that is not from USA/UK.
Additionally I am not speaking about substituting the imperial system but just put in parenthesis the values of non-USA units so it is easier for the rest of the world to visualize.
I am loving the new PF2. I am just a little bit concerned about the "weight" of the level bonus compared with ability or "training" bonus.
I understand what have you done. You have tried to simplify and merge skill and attack bonus, as long as it is just to calculate a modifier to get through a DC. I think that this makes lot of sense and reduces the complexity of the game without affecting customization/fun.
The problem is that while in combat it makes sense that the experience (level) becomes key for skilled people, for skills ... well training should be more important.
So far at lvl 6, for skills, a character can get a +6 from level,+3 characteristic, + 1 training, +2 item). A + 12, where the 50% of the bonus is due to level. The items can be purchased, therefore, the 75% of the bonus is due to the character level.
Then I understand that to counter that you have said that the skill level "untrained, trained, expert" it is not only about the bonus, but also about what you can done and skill feats. Good idea. The problem is that in my opinion, especially the first, makes the game too complex, as GM tunning one parameter, DC, it is easy, but tunning 2 parameters DC and training required might be a little bit challenging.
So I would propose that instead of getting a +1/level, you get a +1/even level and double the skill training modifiers.
In the previous case, for instance, now the PC will get (+3 level, +3 characteristic, + 2 training, + 2 item) a +10, where only the 30% of the bonus is due to the level.
Could this system be applied also to the combat? Well, this could be done, but it might be tricky. The problem with this is that you will get the same AC, and then decrease on the attack bonus might hurt your hitting chances quite a lot. Of course, we could decrease the bonus of the armors, and while this might work for heavy armor, this wont work for DEX based AC. Furthermore, when you have magic items, the armor bonus to AC becomes less important. We could change the system so heavy armors provides apart from AC, DR or critical hit protection. But from the mathematical point of view i see difficult to find a balanced way to do it.
So, my opinion, is that it will be better to have two proefficiency bonuses, 1 for saves and combat (i dint discuss this here, but yeah, it is similar), and other for skills.
Additionally, I think that neither on PF neither on PF2 is is highlighted enough the neccesity of circunstancial bonuses on cross-skill checks.
For instance, is you want to sneak around a guard, you roll stealth vs perception. However, it should be taken in account the circunstances, if its day, or night, or things like that.
Finally, regarding the accumulation of bonuses, I would suggest to simplify it basing it on the "source" than on the "type". For instance, a system where you can only add three type of bonus, the highest coming from the item (even if they are different bonus type), the highest coming from the circunstances, and the highest coming from you (spells, ancestry,..). Sometimes it becomes a little bit annoying to make the checklist of the bonusses you have. This will simplify the calculations.
I like your policy to include diversity in the game as this represents our society and what is more important, welcomes everyone to the table.
However, I find pretty difficult using the imperial system as I have never used it. It is pretty tricky to keep in mind the different conversion rates (1 inch 2,54 cm; 1 m 3´, 1 mile 1,6 or 1,8 km depending on what type of mile are you using, gallons - liter, pounds - kg, ...) and googling them slows the game.
What about referring to both systems so the rest of the world have it easier?
Bite—injury; save Fort DC 10; frequency 1/round for 4 rounds; effect 1d2 Strength damage; cure 1 save.
This means that if the spider bites one of the PC, he needs to make a fort DC save if he fails, he will suffer 1d2 strength damage.
a) If the PC is not bitten next turn, he needs to roll again DC10, to avoid further 1d2 strength loss? or he needs to roll and if he saves, he has the 1d2 strength back?
b) If the PC is bitten again next round
b1) Does he the right to roll fortitude 10 before, to see if he can get rid of the poison of last round?
b2) Does he the right to roll fortitude 10 for this new poison (to avoid getting inside his body)?
b3) He roll just one once at DC 12 (stacked poison)?
b4) He just roll DC10 for the new bite
- If he succeeds, he avoids getting the new dose of poison inside, but still has the poison of the last round inside, and therefore he needs to roll DC 10 again.
- If he fails, he needs to roll DC 12 for both doses, succeeding means that both doses are eliminated from his body.
C) Imagine that he fails all fortitude checks, after the duration of the venom (4 rounds + 2 rounds/extra dose), he gets his strength back right?
D) Englishwise, did I use correctly the word "poison" or should I have used the word "venom"?