Ukraine attacks Transnistria and asks Romania to open a second front, but it is Russia that is preparing the invasion of that it has already invaded....Brilliant logic!
AFAIK, the British intelligence recommends Ukraine not to, because it is going to produce an imperative for both Russia and Transnistria to attack both Nikolaev and Odessa, making Ukraine a landlocked country for good.
You’re making the case for Ukraine and Moldova to preemptively attack and destroy the Russian forces in Transnistria. As well they should.