Well, that might not be a clever strategy.
If you expect ideas to be ready, well defined, proper ROI calculated etc you will get a behaviour following this expectation. People will spend more time working with their ideas. Polishing, preparing, powerpointing, details added, risks handled, marketing explored.
All to make a brilliant, shiny and excellent presentation so that you can understand the idea and buy into it.
But, what now also happens is that the person with idea will spend a lot of time and effort with his idea. When you spend time and effort you will hate to see it ruined. And you will also most likely fall in love with your idea, especially since you have covered all angles and perspectives. "It's a brilliant idea. I have it all covered." (Sure you do. But only from your perspective....)
So, now you have a person that spent lots of time on his idea. And really loves it. How will he react to suggestions? Criticism? Alternatives? Questions? "My idea is perfect. Look here...and here... and here...And I also have spent a lot of time on this!"
There is also a risk that when you see the idea you take this into account. "Oh, he spent lots of time on this - Let's be careful when dealing with this." And thus accepting to move forward with a bad idea - only to be kind.
So, if you expect ideas to be ready when you hear them you will foster an organisation that delivers shiny ideas - carved in stone - hard to adjust - and possibly worthless.
Expect high quality - and you might end up with no quality at all.
Better to encourage people showing their ideas early - and raw. Help them build upon the ideas. Support them. Do not expect a finalized business case - help them build the business case.
Adjust the direction of the ideas. Get expertise and right knowledge involved.
Expect any and every idea to be raw. Support the development of the idea instead of analyzing and judging it (too early). Let the judgement grow - while you together explore the idea.
Expecting ideas to be "raw" works amazingly well for ideas that actually are shiny and ready too.