Sorry, I haven't been "in the mood" to do things for a while now...
The Template:External could be used as is, unless you have any different opinion on the looks of links (basically they show as times font - or similar, depending on computer - and in bold weight).
I have no real idea on how to do a working, and practical, code template, as there are a couple of quirks in the Wiki system I haven't gotten around:
- Equal signs do not work in template calls
- Line breaks do not work either
Perhaps your example (How to import playlists) of hard-coding a table really is the best one!
Regarding the spam blacklist I'm not absolutely sure how it works - is there anywhere I can read up on it? (OK, I see what the comment on top says, but I'm old enough to know I might not read it as intended - so I'd prefer a bit more info if there is any out here!)