This is a tough choice for me. A part of me wants to say reboot but another side says no. But I want to give you my Pros and Cons in order for me to decide this one out.
Continuing The Story Following The Events of SCV
Pros:
*The new characters from SCV will get a second chance to flesh out
*The entire story mode that Project Soul had planned will explain everything that we as fans have been debating for a long time (i.e. If Viola is Amy, Leixia and Xiba are Kilik's kids with Xianghua, The Malfested angle, and Z.W.E.I.'s origins)
*Bringing back old play mechanics (bringing back the old Guard Impact)
Cons:
* There may not be a Soul Calibur VI should either Project Soul don't announce it or worse, disband.
* Fans are still crying foul for every other reason
*Namco Bandai is treating Project Soul like a stepchild in favor of Tekken right now.
Fill in the story between SCIV and SCV
Pros:
*All our mains return
*A suitable time frame (set a year or up to 5 years the maximum)
*Getting an in-depth look at what really happened all those years in between and possibly rectifying them by altering them before the events of SCV take place
Cons:
*Although it will be a sequel to SCV, many people will somehow confuse this for an alternate timeline, which is not. So to clarify the timeline, it would be SB/E - SC - SCII - SCIII - SCIV - SCVI - SCV (Think about how Street Fighter did their timeline from SFA- SF1- SF2- SF4- SF3)
Reboot the series starting with SE
Pros:
*All our mains return including characters from SE, who deserve a complete makeover in terms of design, moves, etc.
*A long (and I mean LONG) storyline that should be told through Edge Master (from SE to SCII), Zasalamel (from SCII through SCIV) and Algol (from SCIV to preventing the events of SCV from happening or at least altering them)
*A long roster complete with tons of single player content and other cool stuff (like bringing back Museum Mode, Weapon Master Mode, Exhibition Mode)
*Endless hours of replay value
*Guest characters could possibly be DLC
Cons:
*It would take a lot of time and money for Namco to shelve out to Project Soul to make this happen
*They would have to add every character and appease the fans plus making sure every character has a different style
*Project Soul would have to bring more than their A Game if this is to happen but only that should Project Soul decide to join a new gaming studio or somehow get fans to petition to Namco, it may or may not work.
Prequel before the events of SE
Pros:
*A possibility of having minor characters like Kong Xiuqiang and Chai Xiangfei as well as ancestral characters of other established characters come in the fray
*A possibility to learn the origins of Soul Edge and possibly Soul Calibur
*We'll also learn if any of the ancestral characters were the parents of the established characters
*Diving more into the Soul series lore even further.
Cons:
*A slight disinterest in people wanting to play a game without their mains being in it despite that they have the same moves as the established characters
*Some will disapprove of this as a means that the series is taking yet another left turn away from what the fans want while some will be enlightened to know more into the Soul series lore.
So there you have it, My pros and cons for each one. So, if I had to choose , it would come down to either a reboot (most likely the possible choice) and tie between what happened between SCIV and SCV or continue onward from SCV (but with more content for story mode to unravel the truth more).