If there are no multiple positions for each insertelement we can do something like:

i = 0;
Insert[origlist, "mark", insertpositions] /. "mark" :> (++i; insertvalues[[i]])

if, there are it can be exteded easily, by making duplicates in insertelements or to make different "marks" for them.

If there are no multiple positions for each insertelement we can do something like:

i = 0;
Insert[origlist, "mark", insertpositions] /. "mark" :> (++i; insertvalues[[i]]) 

(*insertposition should be sorted*)

if, there are it can be exteded easily, by making duplicates in insertelements or to make different "marks" for them.