Spare wheel for indoor trainer use
You should be fine using a 105 cassette on the turbo wheel. There will be wear to the chain, cassette and chain rings, but provided the drive train is clean and lubricated then this should be minimal. Doing what you've suggested is a good solution. Try to make sure if you use the bike on the road then the drive train is reasonably clean before swapping onto the turbo wheel and if one cassette becomes more worn than the other then replace it, or you might then have problems and cause more wear on the chain.