If a map is good, and someone has the ability to find the modders neccessary to speedrank it, then there shouldn't really be a problem.
The reason maps get speedranked is that the mapper is known as a mapper that knows what (s)he is doing. For instance, when I send people my map to mod, I've built up a reputation as a mapper who doesn't know what he's doing, so many people will just ignore me. Now if I were to tag a big "ztrot" or "DJPop" name on it, I'd get a bunch of mods. Because, you know, they're good maps. Good maps that people will enjoy and should be ranked. People are also inherently lazy, so they'd rather mod a map from someone that they know will probably be really good rather then a map that will require a giant mod post.
The only problem I have with speedranking is if the map actually isn't very good. What people assume when they want to say "STOP SPEEDRANKING" is that they want really skilled mappers to make a great map, and then stare at a brick wall, and then get their stuff ranked.
osu! is a game, and the sad truth is, not everyone is going to get their maps ranked evenly. Hell, I've been working on Listen!! for 1.5 years, and it's not even close to being ranked atm. But that's because it still have its issues. Every mod post I get will say stuff that I find relevant to change. I very rarely get a "this map is good, star~" post, because the map just isn't top quality. osu! should have the best of the best maps ranked, and if that means that it all comes from a few people, then that's how it is.
The way I see a map's rankability is if
A) The map plays well
B) I can find no technical problems
C) If it's fitting to ranking criteria
if a map fits that in 5 days, 5 weeks, or 5 months, it doesn't neccesarily matter. Everyone is at a different skill level, and can produce quality maps at a different rate. There shouldn't be a limitation to how fast a map gets ranked as long as its a quality map. If there's unrankable crap there, then that's when it starts sucking.
I literally just woke up, so sorry if this argument isn't formatted the very best.