I tried ! and that would be a neat composer-preview-redux-in-OP kind of thing but… 
I must be missing something, if I understand correctly the Reply Template component takes the raw and looks for “replacers”, but the Placeholder Forms component decorates the cooked?
What I’m trying to do is ease my users into adding some quizz Q&As in a topic, with minimal technical friction, clicks or even key strokes, :heavy-sigh: 
[wrap=placeholder key="question" description="question"][/wrap]
[wrap=placeholder key="réponse" description="réponse"][/wrap]
[wrap=template key="template-spoiler" action="reply" tagsList="#qui, #quand, #où, #comment"]
## Question
=question=
### Réponse
[spoiler]
=réponse=
[/spoiler]
---
*Étiquette(s) ?*
[/wrap]
which gives
so far so good, but unfortunately, the placeholders =question= and =réponse= are kept in the composer when hitting the template button