By my understanding, yes I think you could turn a Mirror that is copying a Tech 0 or 1 unit back into a Mirror with Manufactured Truth, and then probably use Quince midband on it.
The question is… why? There are such edge-cases where that would be relevant, that I struggle to imagine it ever being useful. And even then technically yeah I think it does still get trashed end of turn/when quince or the original dies, because those things are stipulated by Quince when he triggers the abilities in the first place.
This is not like the Prynn case where you can prevent units returning from the void by delevelling her, because Quince appends the trash conditions to the Mirror at the time of copying, rather than it being a triggered ability by him at the time the conditions are met.
Ok actually while writing this post I realised you could use Manufactured to turn a Tech 0 or 1 unit into a Mirror and then use it to copy a Tech 2. So ok it has niche application, and is still rarely more useful than just using the Mirror you already have (because Manufactured Truth requires the thing to be on the field to be copied). Maybe if your opponent has a Mirror and you’re short on gold…? Man I dunno, I’m not gonna spend any more time thinking about this because it’s pointless in 99% of cases. If an edge case like this comes up in a game and I’m judging, yeah I’ll rule it as best I can.
Point being, no you cannot use Quince Midband on a Mirror Illusion that is copying something else, because it is no longer a Mirror Illusion.