The carrot is that Russia will probably be allowed to keep their ill-gotten gains in Ukraine. Some sanctions relief might be on the table as well. Dealing with a stupid, yet dangerous state like Russia, a carrot only works with a stick. All your suggestions effectively allow Russia to be even more brazen in its imperial ambitions going forward. That would be a big mistake. Conquering land needs to be prohibitively expensive. And for the sacrifice Ukraine is giving,they need proper assurances that they won't be attacked again a few years down the line.

European troops in Ukraine, adding them to a new European nuclear umbrella, and giving them a pathway towards EU membership and a "Marshal Plan" to rebuild are the kinds of things Ukraine needs to feel any kind of confidence in a ceasefire or peace agreement.