(See the best response by Kaiochao.)
Not a code problem, per se.

Problem description:

I'm working with a game that uses a very small default tile, which has the side effect of making any icon used as a mouse cursor shrink down to an equally tiny size.

Is there any way to override this and explicitly set a mouse cursor size other than by changing the default icon size?
Best response
Related feature request:

Forum_account's Mouse Position library lets you easily use a screen object as a mouse cursor. However, using that library means you pretty much can't click anything, because BYOND doesn't have native support for detecting mouse position.