Little late on my reply (Got swept up during the weekend.). While I would love to see Arius in DmC, I wouldn't want him to be the main antagonist. At this point he would be just be "DmC Mundus-Lite" since they both use the "Big-Business" Shtick. However, it could work.
Say Arius was Mundus' right-hand in business (Since its pretty obvious Mundus isn't the type to let competition walk around freely.). Maybe, in the first DmC Arius was CEO of a Faux Rival/Competing Company or a Forgein Branch of Mundus' company.
(Following
@TWOxACROSS 's one year later scenario.) With Mundus out the picture at the end of DmC, Arius tries to pick up the pieces, Dante goes "LoLNope.jpg", kicks down his door, "Start DmC2 Mission 1". Would be a hell of a start having Dante fight a big bad (or his wall of security) right off the bat and show how much Dante has advance in one years time.
On the subject of Arkham, like what others previously, he could work the same way he did in DMC3. Hell, in DmC in terms, he would be Vergil's Phineas (Sans his ulterior motive, of course.)