The main problem as I see it, is that IMO the PBEM genre is actually dying in Civ4. There are just way better MP opportunities including PitBoss. While PB enables to play games with many players, these games have too many players and too large maps making a reasonable military win essentially impossible while it were quite doable in CIv3. That is the nature of Civ4 as a game and this nature basically sucks to a certain extent.
Also, excellent scenarios in Conquests had provided ppl with endless hours of fun playing the MP versions of these. This stuff is just not there with Civ4. Another problem with ladder-type things is the great difficulty of mapmaking in Civ4. It is not impossible, it is possible but making a fully custom map takes horrendous amount of time. While map generator is OK, it still has numerous glitches and if you are left without copper or iron, you know what happens. Thus, even though there are many successful PBEMs finished, as I said previously, the genre is not what it were in Civ3.
So, in terms of features and site development, what I would like to see while agreeing completely or partially with POV of other ppl posted above is
1) More "small" PB games with 4-7 players on smaller maps.
2) Some type of regular turn-based or simul MP games without any timers may be with subs played once a week for 3-4-5-6 hours (Friday night) again with 2-3-4 up to 7 players max.
3) I'd greatly like some PB or PBEM BtS scenarios played out. May be some other scenarios or mods.
4) Forum upgrade. Unlimited (or large) number of smileys in a post is mandatory however. That spam is too good to be erased. besides, no other forum has it.
5) I don't care about front page or fancy stuff or chat.
6) No ladder for me. There were enough of that besides it is somewhat childish. If I want a ladder I'd go for GOTM in SP or PAL in MP.
7) Finally, keep them spoilers coming.
