Only Russian absorption or total annexation is a 'permanent solution'. A "paper treaty" formalizing neutrality is a useless formality as nations can break international law anytime they want. It's only 'legally-binding' to extent either party respects the treaty. Russia needs a permanent veto over Ukraine foreign policy, where a paper treaty is as good as toilet paper in this day and age as nobody respects the international law anymore.
Using this logic, Russia should have invaded Poland, Baltic states, Hungary, and Romania to forestall "long term loss of strategic autonomy" because NATO troops directly bordered Kaliningrad and region near Saints Petersburg, and even closer to Moscow than Ukrainian border in 2003.
BUT.... Russia was weak back then. Now it's stronger. So it's ultimately a "Might makes Right" argument right, not some 5D chess strategic calculus about losing autonomy, Russia lost autonomy when Baltic states joined and NATO shared a border with Russia in 2003.
Sometimes nations do things against their economic interest because of perceived security interests. So it's ironic that you say US is throwing good money after bad, but somehow Russia is getting good money for a useless paper treaty neutrality. Russia needs to annex or install a puppet regime to make all these sanctions worth it. A paper neutrality treaty is a useless formality without regime change. Russia needs to topple the regime to have permanent long-term security.
