I lived without a garage/enclosure on a lake where horrible wind, floods, bugs, rain, "nature crud," and spiders ruined and weathered everything. I looked online for enclosures and small buildings that would also be convenient to ride in and out of frequently. Many sealed hard plastic motorcycle enclosures were $2/3k+ and sold overseas. A zipper bag enclosure/bubble would get absolutely shredded by wind and water where I lived. I finally considered getting a small and cheaper trailer with multiple use cases! It cost me around $3600 but is also incredibly useful for many other uses as well (moving, transporting large objects, etc). I installed rubberized flooring and a condor wheel chock inside as well. The large door helps me easily ride in and out with a convenient side door for working on the bike. Even a year later, the inside has remained completely "sterile." No bugs and is dry with low humidity. Consider an option like this if you don't have space for a new building, don't have a garage, or would have use for a trailer to begin with.
edit: as discussed below, always consider the level of crime in your community to determine whether or not something like this would work for you.
I will admit that the area that I lived in had nearly zero crime. Rural. Regardless, the trailer walls have a steel skeleton that are slightly more difficult to cut through than just the wood and thin sheet metal exterior. I use a pretty tough set of wheel locks and a hitch lock. But yeah you're right someone could definitely take what they wanted if they are already used to cutting into other trucks. It is definitely safer than leaving the bike outside, right? Or do you think the fact that it is a trailer would make it even more of a target than a covered motorcycle?
Out of sight is for sure better then plain site. Chances are you would have nothing to worry about especially since tools are not that quiet.