I feel like 1/4 of the roster of DoA5 are "guest" characters at this point, coming from VF and Ninja Gaiden. Then again, the latter group was there since quite some time, no?
The only Ninja Gaiden characters are Hayabusa, Rachael ,and Momiji, but Hayabusa has been there since 1. There are only 4 VF characters, Jacky being the last one added due to popular demand. The newest members of the roster are Mila, Rig, Marie Rose, Phase 4, Nyotengu, and Honoka. Raidou is a returning character from DOA1.
Also I wouldn't count any of the Ninja Gaiden characters as guest, since it's the same company.