If the application is simulating a crisp higher-resolution image that was slightly blurred while downscaling to the output resolution, a linear color space is exactly the right choice. Yes, it means bright objects on a dark background will look larger than the reverse, but that's just a fact of human light sensitivity. If the blurring is purely optical, with no pixels in between, a small light in the dark can still create a large halo, whereas there's no corresponding anti-halo for dark spots in a well-lit room.

On the other hand, if you want something that looks roughly the same no matter which color you use, counteracting such oddities of perception is certainly unavoidable.