I'm with moshu and resiny on this one.. =P Talk about days and hours of mass file editing to get this done the way you want it sigh. =/
I'm just thinking about it now, changing all the WordPress files to recognize the: wp-login location, and then possibly going through all the plugin files to do the same, then maybe even the theme files as well...Eeek.. forget about all that work lol.. =P
I do know what you're talking about though icyflare. =) Kinda does sound or seem like something "cool" to do or whatever, but just too much work for me, if only it was easier..sigh
Well, there is that little program thingy that Podz mentioned about for changing certain text in all files of a "directory" on your PC to whatever text you want it to be for. But I dunno..
SCR 1.0.002 Freeware edition (13KB) . Use that to search and replace your website url with your Xampp url.
But instead of replacing the "url" within those files, you'd just be changing the wp-admin to wp-login.. Again, I dunno about that though..