unlockable content I think should be available in DMC5:
Dante: DMC 1-4 and teaser costumes, DMC1-4 and teaser coatless, Sparda costume, vestless DMC1, Topless DMC1, Diesel costume(no stupid neck scarf) DmC(with classic Dante hair), DmC hood up, Neo Dante(I liked it. sue me. it has Classic Dante’s hair though) DMC1 Dante’s costumes have Rebellion instead of Force Edge and he gets a DMC1 style Rebellion DT for that. LDK costume.
Nero: DMC4 costume(normal and hood up), DMC4 coatless(normal and hood up), DMC4 vestless(no coat, no vest, just the black undershirt), Shirtless Nero(no top at all, to show off the DB and how it connects to him), White Order Nero(from the concept art, hood up), Blue Order Nero(from the concept art, hood up)
Lucia: DMC2 Costume, Secretary outfit, DMC2 capeless, DMC2 Diesel outfits
Trish(unlockable & side missions): DMC1+4 & anime costumes, Eva costume, Gloria
Lady(unlockable & side missions): DMC3+4 & anime costumes, DMC3 alt costume(the white one), red biker suit from the anime, Kat costume
Vergil(unlockable and side missions): DMC3 costume, coatless, Corrupted Vergil, DmC(with classic Vergil hair), DmC(coatless)
Sparda(unlockable & side missions): Coatless
Berserker Dante: unlocked after beating Dante’s extra missions that take place in his mind and his inner struggle to regain his sanity after his DDT is released. After "beating" Dante, you regain control of Dante to take on the Berserker. He is more stoic than Dante and has a twisted sense of humor. His personality is similar to Kenpachi Zaraki from Bleach, but is a bit more serious and looks for a kill rather than a fight. His fighting style is much more brutal, ruthless, and sadistic than Dante’s. He has black sclera and red eyes. He has his own moves and a new style or two. His Devil Trigger is the DDT
Berserker Vergil: basically its Corrupted Vergil but no Yamato, just the Dark Angel blade and a different outfit with a cloak that looks like Nelo’s cape. Any gauntlet weapons are replaced with Nelo Angelo’s gauntlets and Grieves. His fighting style is a much more brutal version of Vergil’s style. he has his own moves and a new style or two and his DT is the one from the last Nelo Angelo fight in DMC1
Boss Rush Mode: Selective Single Boss and Rush Mode
Bloody Palace: Normal and Time Attack
Cutscenes slightly change to accommodate the costume if need be, but the standard DMC5 costume cutscene is canon
Theater Mode: can select which costumes you want to see in the cutscenes
for further customization possibly mixing different parts of different costumes. For example DMC1 vest with DMC4 coat with DMC3 pants with DMC2 hair.