No. I don't think it's appropriate to add it. Besides Arcane Spell failure chance is pretty much only due to armor.
Why would you be wearing armor when you're not even proficient?
Besides the ability is about when your spell fails because of enemy defenses, not because you couldn't move right in your armor.
Even if Rewind did work to avoid losing the spell, you'd still be occasionally losing your entire turn over arcane spell failure. This is just not something you can abide by in a combat situation. The only real way to use heavier armor on an Eldritch Knight build is by slapping Still Spell on literally everything that has somatic components. By and large it's better to just manage your AC and accept that it won't be as good as someone wearing proper armor.
Do remember that Mage Armor isn't the end of your defensive buffing options as a Wizard, but rather just the beginning. Shield spell is another +4, Cat's Grace gives +2 from Dex, and there is nothing wrong with rings of deflection or amulets of natural armor. Then you have defensive spells like Mirror Image to add forms of defense that aren't AC. You'll have to manage your daily resources and keep track of lots of durations, but there are plenty of options to help you out here.
Why would you be wearing armor when you're not even proficient?
The non-proficiency penalty only applies to attack rolls. If you're primarily using spells that call for saves then non-proficiency has no ill effect. ASF still makes it a no-go for arcane casters, but Psychic casters who have the strength for it can absolutely make use of the non-proficient armor option.
So I'm playing a dwarf fighter wizard thinking of taking the Chronomancer archtype. They have the ability to rewind time to regain their spells when they fail. One reason they might lose spells not listed is due to Arcane Failure. I'm wondering if this was omitted by intent or mistake and if it should be allowed. I think it should since every other reason a wizard loses his spell is listed.
You've correctly pointed out that arcane spell failure is not covered. Unfortunately, questions as to whether that was intentional are going to be a guessing game as Paizo has turned their attention elsewhere and is no longer answering questions about Pathfinder RPG rules. Play it however you think is best at your table.
And don't put too much stock into folks telling you that you're Doing It Wrong™. There's nothing inherently wrong with playing a character with a nonzero arcane spell failure chance. I've done it myself and it's perfectly fine.
And don't put too much stock into folks telling you that you're Doing It Wrong™. There's nothing inherently wrong with playing a character with a nonzero arcane spell failure chance. I've done it myself and it's perfectly fine.
I would strongly disagree; losing turns to percentile dice is one of the least fun situations you can back yourself into. I'm not a fan of the way ASF works and I feel it's far too punitive, but as written it's not something you want to mess with. There's enough ways for the random dice gods to screw you over as it stands; you don't want to add self-inflicted failure to the mix. People are free to do whatever they want, but that doesn't change the fact that such a character can be incredibly frustrating.
Arcane Armor Training isn't a particularly good feat line, but with mithral breastplate it at least works.
Mea culpa, I missed where he said he was a fighter for some reason.
Even with proficiency, arcane spell casters shouldn't generally wear armor.
If you want to cast in armor, pick up Arcane Armor Training feat and Arcane Armor Mastery feat. That'll get you down to 5% Spell failure chance with breastplate. Mithral will make that 0.
It does however cost you a swift action each round you want to cast. But maybe that tradeoff is worth it to you.
And don't put too much stock into folks telling you that you're Doing It Wrong™. There's nothing inherently wrong with playing a character with a nonzero arcane spell failure chance. I've done it myself and it's perfectly fine.I would strongly disagree; losing turns to percentile dice is one of the least fun situations you can back yourself into. I'm not a fan of the way ASF works and I feel it's far too punitive, but as written it's not something you want to mess with. There's enough ways for the random dice gods to screw you over as it stands; you don't want to add self-inflicted failure to the mix. People are free to do whatever they want, but that doesn't change the fact that such a character can be incredibly frustrating.
Arcane Armor Training isn't a particularly good feat line, but with mithral breastplate it at least works.
Losing turns to failed spell resistance checks or successful saving throws isn't any more fun, the number of sides on each die notwithstanding, but we get by. Yes, they have mitigation, but then so does ASF, and neither are absolute. It's a tradeoff that may or may not be worth it depending on the character concept and build.