billd91
Not your screen monkey (he/him) 🇺🇦🇵🇸🏳️⚧️
The other problem with allowing a character to cast 2 swift action/quickened spells in a round is because that's two spells that don't provoke AoO by virtue of their action type. Normally, when able to cast 2 spells a round, only one of them gets that pass.
In the hypothetical case of a character with a quickened magic missile and a scorching ray who fails to cast their initial attempt at a swift spell, I'd probably let him burn the magic missile as a standard action (subject to AoO), using the spell slot it was prepared in. The spell is prepared with the extra metamagic structure, but rather than invoke it with his normal completion action (swift action), he uses the completion action for the regular casting (standard action). He just ends up not using all of the mnemonic/mystic/whatever structure he built into it.
It may not be in the RAW, but it seems pretty fair.
In the hypothetical case of a character with a quickened magic missile and a scorching ray who fails to cast their initial attempt at a swift spell, I'd probably let him burn the magic missile as a standard action (subject to AoO), using the spell slot it was prepared in. The spell is prepared with the extra metamagic structure, but rather than invoke it with his normal completion action (swift action), he uses the completion action for the regular casting (standard action). He just ends up not using all of the mnemonic/mystic/whatever structure he built into it.
It may not be in the RAW, but it seems pretty fair.