I need a place where if I really have something on my mind I'm free to take a day and explore it. If I think I can improve the quality and codebase I should be

I need a place where if I really have something on my mind I'm free to take a day and explore it. If I think I can improve the quality and codebase I should be free to do so provided I dont break anything or I make all the changes required to implement it fully. Example: I wanted to start to implement std::thread and use of auto. It required us to start using c++11. I should be free to do this, fix anything, make sure devs are set to compile correctly and start implementing. I can do it locally, demo it and then get the green light to merge.