I learned a long ago:
1) I can offer the best ideas that go beyond lines of code, but it usually comes down to the decision of someone in a higher position than me (manager, sales, the CEO, etc) and if they just don't feel like utilizing your ideas, they won't. Fighting this is more trouble than it's worth.
2) Most companies, unless you are in a startup where you wear many hats, don't want you offering your ideas. They have the ideas and want the developer to make them into a reality.
3) Most of the time, a project manager is the person that thinks about the bigger picture. I don't really want to have the responsibility of both roles..without the salary increase that comes along with it.
I love thinking about the bigger picture, which is why I have my own company I'm building on the side. But I would much rather just get my job done as a developer for my day job.
If you combine your idea pitch with a working prototype (doesn't need to be polished), it's odds of getting adopted will be far more likely.
If your idea isn't one that can be prototyped, e.g. "Ask Microsoft for a billion dollars", then you may as well just pitch it, just like anyone else.
If the company is not interested on listening to new ideas, and you're keen on participating in something you would like to help build, then perhaps this is not the right company for you.
Just please be aware that after you've delivered, you loose power for negotiation. Therefore I would probably rethink the timeline choosen for agreeing on a reward "then I can say how much I want to be compensated for..".
But only if you think it will demonstrate enough value to get you something you desire: cool work, a promotion, etc.
This requires a good understanding of what your managers and the larger organization will value, and whether they reward people who show they can deliver on those items. People's careers _do_ get bumped from these kinds of efforts, but I've seen a lot of engineers spend 40 hours prototyping something that management just won't value.
I have a family and only have so much free time. Even if I didn't, why would I spend my free time building anything for a company and not get compensated for it?
Even if you go through all of this, there is no guarantee you will get the responsibility and pay increase.
I honestly don't really care about any of my ideas winning out. I'm perfectly content getting told what needs to be completed and coming up with a good solution.