I am not sure if this right or not, but I always looked at what side something is happening has got to do with tense. Left, being the past, and right, being the future.
Pentacles and Swords, the hand is coming from the left, presumably the past.
Cups and Wands, the hand is coming from the right, presumably the future.
So, for instance, if that is the case, then you would expect the Cups and Wands to happen first, then followed by Pentacles and Swords.
Now, lets look at it this way, say Ace of Wands is when something you would start, that can be seen out of the blue, maybe totally unpredictable, spur of the moment, type thing. Then, if that is something that you want to stick to, then you can start something that would mean that you would put more work into it, to become more viable, thus, Ace of Pentacles.
Say, Ace of Cups, you get new feelings about something, then later down the track, Ace of Swords, you get new ideas, concepts, attitude, thoughts and what not about it.
No idea if that is right, but I figured it was worth mentioning.
