I noticed that verb ending syllables cover all of -u syllables (る,く,ぐ,す,つ etc) except ず,づ, ふ, ぷ, しゅう, ちゅう and じゅう.
I suspect that ず is reserved for the negative conjugation thus no plain form verb is allowed. しゅう, ちゅう and じゅう were mostly reserved for on-yomi pronunciation, I think, so no verbs for them either.
Not sure about づ.
ふ and ぷ is a curious case because there are verbs that end with ぶ but not the other two.
I'm not saying that there should always be verbs that cover each of the -u syllables but I'm just curious why there are no verbs that end with some of them. Maybe there are some historical reasons behind the gap?