Someone you're managing says, "I know - let's do xyz; it will solve the abc problem." If your reflex is to empower by saying, "Super! Go ahead!" let me do a little translation and let's see if we can come up with a better approach.
When people make suggestions like that, they mean one of two things. They either mean that they're ready to go but they're being deferential to authority, or they mean quite literally that they have simply identified an approach of promising (but unknown) relative merit.
In the first situation, the verbal suggestion is really a proposal (or a proposal for a proposal). Having the leader say "Yes, go!" is an acceptance of the proposal. If everyone is clear on this communication, that's fine.
However, my experience is that most people mean the latter, that they've just simply had an idea.
In that situation, the next steps for the leader are:
(1) Need. Be clear as to what need the idea is addressing in the mind of the person who suggested it. Ask them to explain this.
(2) Implementation Plan. Walk them through a discussion of what they have and what they need to execute leadership of this suggestion. Have them describe how they would go about finding resources for what they suggest doing. And they may need to think about it, which is fine of course.
(3) Resource Gathering. If adequate resources are available or they have a solid plan to pursue them - great! However, if adequate resources aren't readily available, and if they don't know how to approach finding resources, and you don't have anyone to pair with them to coach them through this learning process, then they really aren't appropriate to leading the implementation of their idea. It's not going to happen. Let it go - it was a good learning exercise in planning.
(4) Team Formation. Alternatively, if they aren't able to resource their idea but someone else is, then that can be the nucleus of a team, where the person who created the idea is in charge at a tactical level, and the person resourcing is an advisor. (The one who thought of the idea has the most context, so should make decisions on the fly.)
I hope that helps.