Well, these are my ideas/recommendations for SCV. Sorry if they're reposts.
1. Characters - Add all former SoulCalibur characters. Li Long, Hwang, Edgemaster, etc. Diversify all clones. (i.e. Rock-Astaroth, Amy-Raphael, Kilik-Seong Mi-na, etc.) It truly feels that Amy stole Raphael's moveset and made it better. Some of the bonus characters in SCIV like Shura and Ashlotte had viable storylines connected to the main story. I'd like to see them return, but a unique moveset. (Seriously, Shura had 4 swords! Badass.)
2. Stages - SCIII had more stages, so I felt a little disappointed with SCIV. I think every character should have a unique stage scattered throughout the world. Almost every character has a background from different parts of the globe. Though, the one thing I found nice with SCIV was the interactive environments, particularly with that circus stage (Forgot the name). It would be awesome to see this extended in SCV.
3. Single Player - Please improve the main storyline. Both SCIII and SCIV's story was pretty weak compared to previous installments. To me, a big draw to the franchise was the unique story. Almost every other fighter out there has no plot whatsoever, but SoulCalibur actually makes it work. Perhaps instead of having non-canonical endings for every character, make everyone's ending connect to a greater, unique plot such as BlazBlue. Add a training guide like in SCIII and SC:BD to help new players get acquainted with the game. Add something similar to Quick Match from Broken Destiny. It was excellent fighting the AI with a specific fight style to help improve my game. Bring Survival and Time Attack back. I think this should be a given.
4. Multiplayer - IMPROVE ONLINE. SCIV was the first to bring online to the franchise. It was good overall, but there were some problems. Make a better netcode and it entice more people to play SoulCalibur. Bring Team Battle back. Bring back replays and add a replay channel. Replays can capture the best moments in SoulCalibur! Like in SCII and SCIII, we should be able to pick our weapons with out costumes. They shouldn't be fixed with any particular costume.
5. CAS - In my opinion, CAS has great depth and customization. I mean what other fighting franchises give this kind of customization? Also, a big draw to SoulCalibur is CAS, so it'd be best to improve on it. Add more armor, faces, etc. However, keep the same hitboxes in CAS for all characters. It's kinda frustrating that Astaroth CAS can get away with stuff because of the smaller hitbox. Don't let the armor break to the point where everyone is in their underwear. It just doesn't make sense to see people fighting with no clothing. Speaking of, improve the armor system. It felt awkward and somewhat pointless in SCIV. I'd like to see it with how MK9 is handling it; parts and pieces of one's clothing is torn/bloody. It makes it more realistic considering that it is a weapon-based game.
6. Mechanics - The Critical Finish system was an interesting mechanic in SCIV and I think that it should return in SCV. However, the orb that determined the soul gauge should be changed or, at least, improved. It was hard to determine when someone was going to be critical finished when the orb simply changed color. Also, instead of cutting to the critical finish per round, maybe the critical finish can only be activated in the final round or when a player is going to win the match in that round. If a player is guarded crushed outside these circumstances, maybe the attacker could perform an automatic combo done only when a player is guard crushed. That way, it won't ruin the flow of the game and it could give the victim a chance to come back from the crush. Also, the tag system in SCIV. It was interesting to see and it would be awesome to see it again with additional balancing, of course.
7. Misc -
I'd wish to see remixes of these three:
Hubris
http://www.youtube.com/watch?v=SvZyfYjuLdU
If There Were Any Other Way
http://www.youtube.com/watch?v=3UUz-8QYm-E
Confrontation
http://www.youtube.com/watch?v=xr4aQj_rGgo
Finally, DLC and support post-production. It will make you guys more money and it will show to the rest of fighting game community that SoulCalibur is a contender, not a shadow of Tekken. It will keep the game alive and prevent from dividing the community. Even though our community is not as large as Tekken or Street Fighter, we can show that SoulCalibur is a serious fighting game.
EDIT: Just thought of some cool ideas. Bring the titles from Broken Destiny back and have that visible (along with other stats like win/loss, most used character, etc) when you fight other people online. I think the titles in BD were really unique and they showed who completed what challenge. Also, perhaps when a particular character fights another particular character, they should have a specific opening for that situation like when Cervantes faces Ivy; they should have a special intro that shows the "intensity/importance?" of the battle. Then, of course, there should special endings too, similar to the critical finish endings; they should only occur under certain conditions such as if Cervantes defeats Ivy or vice versa. Like Destined Battles. Speaking of, Destined Battles should return too. Those made the story mode more engaging.
EDIT2: How about adding a Sound Test Mode so we can listen to our favorite tracks without having to play the game? Music is a huge draw for SoulCalibur and adding that would allow players to listen to the music without interruption or noise. Also, even though even music is added in each sequel, going back and remixing classics isn't bad either. For example, the Castlevania franchise remixs their tracks in nearly every game, but it's done in such a way that it feels new or exciting to still listen to. I'm not saying that the whole soundtrack should not have anything original, but there's a lot of classics that we as a community love and would like to see return.