Buffer, yes. But the Maidan protests started because Russia made the first power grab. The very openly pro-Russian government of the time had just passed legislation that put Ukraine on a direct path towards becoming what is now Belarus. TBH, if that hadn't happen, we'd just have Ukraine more or less locked by Putin now. So no, we're not talking about a buffer zone, sorry. Not even in the strict military sense - the invasion today came from Belarus as well, and some reports even claim Belarusian troops, not that it matters much. So without that regime change, we'd most likely see Ukraine as part of the Russian Federation in a military capacity as well.
We _had_ a buffer zone until yesterday. NATO was supporting Ukraine without much real intention of having it join, while Russia had Crimea and half of Donbass. This could have gone for decades - see Transnistria, which does exactly the same for Moldova for 30 years.
From his wikipedia page, copy/paste the section "Exile in Russia". Nothing added or deleted:
According to Russian politician Oleg Mitvol, Yanukovych bought a house in Barvikha for $52 million on 26 February 2014.[215]
On 27 February, a report stated that Yanukovych had asked the authorities of the Russian Federation to guarantee his personal security in the territory of Russia, a request that they accepted.[216] Yanukovych claimed that the decisions of the Rada adopted "in the atmosphere of extremist threats" are unlawful and he remains the "legal president of Ukraine". He accused the opposition of violation of the 21 February agreements and asked the armed forces of Ukraine not to intervene in the crisis. The exact whereabouts of Yanukovych when he made this statement remains unclear.[217][218] He later thanked Vladimir Putin for "saving his life".
On 3 October 2014, several news agencies reported that according to a Facebook post made by the aide to the Ukrainian Interior Minister, Anton Gerashchenko, Viktor Yanukovych had been granted Russian citizenship by a "secret decree" of Vladimir Putin.[219] On the same day, Russian presidential spokesman Dmitry Peskov said that he didn't know anything about this.[220]
In 2017, Russian media suggested that Yanukovych is apparently living in Bakovka near Moscow, in a residence owned by Russian Ministry of Internal Affairs.[221][222]
On 26 November 2015, Yanukovych received a temporary asylum certificate in Russia for one year; later extended until November 2017.[223] In October 2017, this was extended to another year.[224] According to his lawyer Yanukovych did not consider acquiring Russian citizenship or a permanent residence permits but "Only a temporary shelter for returning to the territory of Ukraine".[224]
We _had_ a buffer zone until yesterday. NATO was supporting Ukraine without much real intention of having it join, while Russia had Crimea and half of Donbass. This could have gone for decades - see Transnistria, which does exactly the same for Moldova for 30 years.