> sometimes they require codec downloads from sketchy looking sites
I'm not sure where you got this idea from, but it is patently false. Although the recommended software for playing anime fansubs is Media Player Classic Home Cinema, which is open source[0], I have had no issues using MPlayer either. And as of 2.0, VLC is supposed to have the requisite subtitle support as well.
It's been a few years since I went spelunking in the anime torrents, perhaps things have changed. But back then, for 32 bit Windows, it was definitely the case that the occasional anime would require an oddball codec. Usually it would be open source but still not be practical to build yourself (if you wanted to watch any anime that evening too).
I'm not sure where you got your anime from, but I've been watching fansubs for the last 10 years. On Windows, VLC has always worked for hardsubbed anime. Once softsubbed anime started coming out, there were some cases in which the font styling wouldn't work correctly, but then you could just use Media Player Classic Home Cinema. As for codec packs, I know some people have recommended installing the CCCP[0], as it includes MPCHC along with some other stuff, but MPCHC by itself has always worked for me.
Perhaps you weren't using a reliable website. I've definitely heard of sites out there that try to trick you into installing spyware by saying it's a codec. I always used torrents to download releases listed on AniDB (I searched using the CRC checksums, which anime fansub groups include in the filenames), so I entirely avoided that problem.
> Usually it would be open source but still not be practical to build yourself (if you wanted to watch any anime that evening too).
As for this, I've never seen any codecs that you had to build yourself, particularly on Windows, so I have no idea what you're talking about.
I'm not sure where you got this idea from, but it is patently false. Although the recommended software for playing anime fansubs is Media Player Classic Home Cinema, which is open source[0], I have had no issues using MPlayer either. And as of 2.0, VLC is supposed to have the requisite subtitle support as well.
0: http://mpc-hc.sourceforge.net/