Well being a huge die-hard NA2 fan, I've been trying to put my finger on the problem for awhile. At least a year, maybe longer. I've played siege in just about every mod available in this game, and CRPG's version used to be the best, imo. And I honestly think we can get it back, but there are a few factors that need to be addressed.
One. Toys.
GK_Siege in Native has stolen a vast majority of former NA2 players. Every time you go there it's packed with near 100 people. One of the reasons I believe is that they've done a fantastic job of implementing "toys" that make siege... siege. Catapults, ballistae, fire arrows, boiling oil, traps, sail-able ships, all kinda neat shit. Now I'm not saying NA2 should copy GK Native, but I do think more toys equals more fun.
Two. Maps.
This is has already been touched on alot so I'll say very little here. However, in addition to the problem with overly huge maps already pointed out, one big factor that's a problem in NA2 is 'not enough' maps. Doing the same maps over and over again gets tiresome. Hell I'll do a few crappy maps just to break up the boredom of the same repetitive map spam. There are alot of good maps that have been submitted in the past that I think need to be brought back. The problem is that very few people upvote a map, but many will downvote. And that causes decent maps to be kicked out of rotation that some just want to whine about. Although I do realize there are definitely 'bad maps' that are exactly that as well.
Three. Multi.
We all play for fun. But we also play cRPG because of the ability to earn gold, gear, looms, stuff. I have tested this and retested this, with several different sets of gear. And the result is always the same. Battle will render 40k+ gold a night for me easy. Mostly due to the fact that gear will only break 'maybe' one item at a time, or none, in most rounds. Siege on the other hand, the rounds usually last longer, causing more chance for items to break. I constantly see anywhere from 3 - 5 items break PER ROUND. And that stacked with less Multi strings = alot less gold. I'm lucky to make 2k - 5k a night in Siege most times. And sometimes have actually lost money.
My suggestion to fix this is hopefully simple - although not sure how easy it would be to code. Instead of penalizing the round's losing team by dropping them to x1 automatically, instead only drop 2 Multis. So for example, "Badass_Duchebag" has a 4x and loses a round. He goes from 4x down to 2x. Or from 5x to 3x. And so on. Obviously 3x would still burn down to 1x.
I think this could be a huge help in equalizing the money gains of siege to battle. As well as make people not want to leave just because <insert map> will result in automatic loss.
Four. Respawn.
This one I'm still not sure about. Smaller pops do need smaller timers for defense, but I don't know if that can be done. I read a suggestion earlier about troop count or tickets. That 'could' work, but you'd need more for attackers most likely, and smaller pops would result in longer battles. But probably still doable.
My thoughts are though, if we take care of 1, 2, and 3... 4 will take care of itself because pop will be larger. However, if the majority of the maps are roughly close in size, the devs would be able to easier average out what respawn timer works best (since you can't make the timer different for each individual map).
Personally I'd love to handle map rotation if no one else wants to take it over for NA2. I do think that someone who loves and cares about NA2, and plays it, should be overseeing that. If there's someone qualified who has already volunteered, and are active, I definitely think it's time to get them in there and give 'em the ball.
Long live NA2!
/steps off soapbox