Actually, I think the optimal decision would be another federation subject on Crimean territory. If they want it so badly. Thought I'm pretty sure their land problems and self-controlling are solvable without that.
The problem is that the entirety of Crimea is Crimean Tatar land currently settled by Russians. I still think that the best way to solve land issues and self determination would be to create a civic Crimean identity that includes the Russians, then create an independent state.
After all, though many Russians seem to see the Crimean Tatars as Muslim Turkic intruders, they're a mixture of everyone that's settled in that peninsula from the ancient Khazars, Scythians and Cumans to the Goths and Greeks and Italians (hence why they are truly Crimean Natives in every sense of the word). Why can't Russians join that mix too?
My preference would be to stop calling them Tatars and just call them Crimeans. "Tatar", though it originally meant something rather different, became a Russian exonym for all Turkic peoples in the Empire. It airbrushes any distinctions and complexities, homogenizing everything. That leads to strange situations where the President of "Tatarstan" has been sent by Putin to Crimea to negotiate with the Crimean Tatars, as if he's some kind of representative from the "homeland", when in reality he belongs to a totally different ethnic group (possibly even Bolghar, if theories are correct) with as much relation to the "Crimean Tatars" as a Frenchman to a Spaniard.
Far better would be to recognise the "Crimean Tatars" for what they are - though they have been Turkicised, they are the native Crimeans, speaking a language that is a mixture of many Turkic tongues and having a diverse ethnic heritage including the peninsula's earliest inhabitants. They're like a snowball that's rolled down a hill.
I would like to see a situation where the native Crimeans can occupy a place in independent Crimean society almost like the Highlanders in Scotland. Nowadays everyone has Highland blood (including myself), though Gaelic can be seen as a waste of money at times by certain bigots and misinformed people, the majority of Scots see it as a part of our complex identity; its prestigious status leads it to be tattooed on patriotic Lowlanders' arms. I think this is very achievable in Crimea, the beast of Russian ethnic nationalism just has to be broken first.