Having mulled over the arguments for and against Archipelago, I still think it could turn out far too easy with Ragnar. He's one of the most entertaining leaders to play imo, but it would be a shame to remove the challenge just to showcase his particular talents.
Financial is HUGE on these maps (even more so than elsewhere), and with long-term water-based bonuses from the UU
and UB, you'll have a massive advantage over your competitors. Throw in the AI's ineptitude on watery maps (esp. in war), and the game could end up as a procession.
Handpicking a few civs would at least give you some half-decent opponents, but I don't think that option is appropriate for an ALC - apart from lacking the surprise factor, it would go too far from the 'standard' civ4 game imo.
And while AggAI sounds like it should make it more difficult to win a warlike victory, I agree with xen01 that it could be way too easy to out-tech your targets before going on the offensive.
Medium&Small might provide the answer, but I've found its maps to be very variable: some are awesome, but a lot are pretty crappy. Big&Small could also give a really good map, but, as you said, there's a chance of getting a pangea with only mediocre islands.
Still, a tough game on a map with a good mix of continents and islands would make for a highly entertaining and informative ALC imo.
Perhaps, as you did for the Persia game, you could get someone to vet a few B&S/M&S starts for you, and select one with an interesting, Viking-friendly, but challenging map (ideally with at least one or two of the other watery leaders)?
Alternatively, if you really want to play an Archipelago, I'd suggest taking it up to Immortal. With two fairly easy wins on Emperor under your belt it shouldn't be impossible, given Raggy's advantages. If you were unlucky with the start, you might get thrashed. But that would still be more fun than a walkover.
