Yeah, I believe it could be, but maybe, seeing that it's based on Japanese, or the Japanese dialgue of the games, "du" may simply be a sound made in the language, Japanese has only around 400 different sounds, as opposed to over 1000 with English, so we may be slicing up words we shouldn't.
Then again, we also have "Lakuto" which is the urgent form, so maybe it does mean something, maybe all verbs in the language are like this, and have different cases, I came up with a case of words based on different verbs I found, and tried to apply similar suffixes to them, and the words I found didn't match any of the vocabulary, which means I may be right.
Lakudu (Help me) = Normal form
Lakuhee = Alt. Normal form (Appears as such in the vocab list)
Lakutal = Formal form
Lakuto = Urgent Form (This DOES appear as such in the vocab lsit, which possibly sparked this theory in the first place)
Lakuyuu = Concerned Form (Maybe as in a Help-me-help-you kind of way?)
Rupurudu (Let's go) = Normal form? (Maybe not, as another list I've read above says this is a formal way)
Rupuruhee = Alt. Normal Form
Rupuruto = Urgent/exited form
Rupurutal = Formal form (or Rupurudu)
Rupuruto = Urgent/exited form
Rupuruyuu = Concerned Form (?)
Wahee (What) = Alt form
Wahtu = Normal form
Wahto = Urgent form
Wahtal = Formal form
Wahyuu = Concerned Form (This came up as "Whayuu: inquiry requesting condition (Phantomilian)")
Turuto = I need (to do something) = urgent form
Turatal = Formal
Turahee = Alt form
Turadu = Normal form
Turayuu = Concerned form
Baryupu (Dancing) = Normal form
Baryuto = Urgent form
Baryuhee = Alt. Form
Baryutal = Formal form
Baryuyuu = Concerned Form?
This is just a theory I have, I might just be trying to force myself to see a connection that may not be there, but I found none of these alternatives in any vocabulary list.
However, there is one word (or set of words) that may potentially break this theory. However, it isn't a verb, but an affirmative, so maybe they have their own set of forms, who knows?:
Jadoo (Affirmnative) = Formal
Padoo = Casual
Dupu = Shortened
What do youse think?