Lots of competent and entertaining actors and artists bloat up and change appearance as they age. Orson Welles. Brando. Have you seen Billy Joel lately?
As long as Frakes successfully conveyed William T. Riker in his last film it shouldn't matter that he was older, red-faced and puffier. The problems with Nemesis
stem from the script and directing, not how fat or frail a character appears.