1. NATO accession is in their constitution, so it will need to be changed
2. They passed several laws in Mar 2020 obligating the state to take back Crimea & Donetsk/Lugansk, so those will need to be rescinded
3. Everybody seem to have forgotten that when the LDNR was recognized, they invited Russian peace-keepers (22 Feb), after which the Russians demanded a cease-fire and offered to settle the LDNR borders at the negotiating table.

The Ukrainians responded by accelerating the shelling, and cutting of the gas and water to Donetsk.