Oooo.... I like your thinking there...
Technically playing a prepared spell caster (Wizard/Archivist) but due to house rules, all Prepared spellcasters are Spontaneous and all original Spontaneous spellcasters use Spell Points instead of Spell Slots (just to keep a distinction between the two)...
Since I have to take Envelope the Wall anyway for Irresistable Spell I may as well put the feat to use for me... and I may as well throw in
Improved Metamagic for another -1 slot thus bringing my persisted spells down to +1(Illusions) or +2(Everything else) and it stacks with itself so I could take it again for free persisted illusions and +1 persist on other spells... Also... I'm not really sure if Metamagic School Focus is really worth taking... it has a limit of 3 times per day and if I'm reading it right it also only decreases the total increase by 1 not each metamagic applied... so I'd only get to use it 3 times per day to reduce a single metamagic cost per spell... the other cost reductions don't appear to have any such limitations though, only the "To a minimum of +1" restriction on most of them... infact it looks like School Focus is the only one that can reduce a cost to +0 all others specify "Minimum +1" and since Easy & Practical Metamagic both only apply to 1 metamagic feat per application of the feat it would likely be more beneficial to just take 4 instances of Improved Metamagic since it applies to ALL known metamagic feats.
That said, I'm not 100% certain if Practical Metamagic will apply in my case, but considering that the house rule also makes spontaneous metamagic rules apply to prepared spellcasters I don't see why it shouldn't still apply... He also houseruled +0 increase and Quicken Spell to NOT increase casting time for spontaneous metamagic... the +0 increase rule only applies to metamagics that had a +0 increase by default or are automatic effects.
Since I can't cast 7th level spells just yet, I'll have to wait a few levels for Arcane Spellsurge... but it will certainly be on my list once I gain 7th level spells. And just because it'd make things even crazier
Rapid Metamagic when combined with Arcane Spellsurge will let me swift cast metamagic spells
That out of the way... I still need help picking which of my 3 remaining eligible spell schools I should prohibit for Incantatrix... and if it's even worth it to invest in Arcane Transfiguration to regain one of my lost schools.