Do not see the problem , it is not a US airline . The engineers and an engine ( if needed) can come from India , if a new engine is needed it will;be delivered to India , not Russia.
As to pax checking the route, and buying a ticket accordingly, good luck, unless you buy it last minute after having access to the filed Flight plan .That said, if you fly on an airline not following the sanctions ( e.g. UAE, Chinese, Indian or Turkish companies, ) you can guess they will overfly Russia if the shorted route is via their airspace.