For me one of the appeals of the "Ryanverse" was the believability. No matter how outlandish the plot it was always believable. The biggest failing, of many, in The Sum of All Fears movie was having Ryan survive a helicopter crash caused by a nuclear explosion and suffer no ill consequences other than a scratch on his forehead.
Clancy's work is grounded in hard science, realistic military maneuvers, and political intrigue. Sum through all this out in favor of action. Will an original script do the same? Probably.
If I were in charge of the franchise I would do a faithful adaptation of Executive Orders. There you have the best of both worlds. With Ryan as President you have all the big picture stuff to satisfy diehard Clancy fans. With the Clark/Ding subplot you have the elements for a good action piece plus a launching point for an action franchise based on Rainbow 6.