Possibly, but that would be something of a 'quick fix'; there is little evidence that Marius' reform was an overnight, sweeping change and it is perfectly possible that the 'new' formations had a large number of experienced personnel in their ranks, reflecting the adoption of what had become quite a standard practice during the on-going wars in North Africa prior to the Germans turning up in the northAs something of a Roman aficionado, I would probably suggest that the 'Generic' cohort ought to have worse stats than the Polybian it replaces. Happy to discuss why I think that in a new thread if you wish.
Since you lose the benefits of organic spearmen, there is already something of disadvantage to them...