I think if you worry too much about rules and such, step on someone's toe then just discuss your idea in here.
Not a bad attitude to worry about being in wrong section at least he is concern and pay attention to the forum rule to post on the right section which is good characteristic of poster with sense of responsibility.
To Op, since the Project Development section is for new ideas, you can simply post there the topic. Even its related to altcoin, I think what you will post I assume probably is the drawbacks and possible unique integration right? At some point when the discussion goes to altcoin topic majority then locked it. Then start a new topic in Altcoin service discussion, to explain and detailed it. Just my opinion.
then I think posting a thread on either Project Development or Altcoin Discussion is enough depending on what you really are up to.
Im not recommending to altcoin discussion, that section is highly spammed thread. If the idea is serious, he can post there but make sure to activate
Self-moderated thread so he can delete spammer's post.