If the West's intention is to weaken Russia by irredeemably wrecking it's economy, the best strategy would be to let Putin seize as much of Ukraine as possible. There was a discussion on a popular Russian YouTube channel yesterday on the economic revival and reconstruction of the 'liberated' parts of Eastern and Southern Ukraine and the sums being discussed were eye watering. These regions, though amongst the most prosperous in Ukraine, were the poorest in Europe even prior to the war- they have seen zero investment since the fall of USSR, most Soviet era industry that remained was rendered uncompetitive after losing access to cheap Russian energy or asset stripped and moth balled by competing oligarchic clans. As an example, the annual budget of Kherson region (1 million inhabitants) per head of population is roughly 1/5th of the mean across all regions of Russia and if the gross figure were to be placed on a league table of Russian regions, Kherson's budget would come second last, ahead only of the Jewish autonomous region which gets a similar amount of money for a population of 150k. If you compare individual heads of costs within the budget, for instance road construction and maintenance, Kherson's average over several years is a mere 1.5% (1 billion roubles vs 77 billion roubles per annum) in comparison to a mid league Russian region with a similar population such as Ryzan. Apparently 70% of Ukraine's power, heating and railway infrastructure (including thousands of bridges just in the East and South) needs complete rebuilding from scratch as it's been left to rot since Soviet times and the rest need major modernisation. The same goes for housing, most of which has been untouched for 30 years. And this is just in the 'better' parts of Hohlandia without even accounting for destruction from the war. All this could cost Russia hundreds of billions and will keep mounting the more territory Russia seizes.
The West would encounter similar challenges in whatever 'Ukraine' remains under their influence but, unlike Russia, there would be no obligation hand out freebies as all the destruction will be blamed on the Rooskies and any assistance doled out will be in the form of loans with strict conditions attached. The Rooskies on the other hand would have to fund everything through grants to win the loyalty of the brainwashed population and ensure they are always better off in comparison to Ukropstan (which is already self evident if one considers HDI, 5x GDP per capita etc)