I think you could look into maintenance training eg http://www.runnersworld.com/race-training/maintenance-training. Also I think Hal Higdon's website has some plans for maintaining fitness between marathons that could be adapted. Or you could train for a slight variation like the Stockport 10 miler in December.
Banking time is the last thing you should be doing. Bank energy instead. In your build-up you most likely will have a test race or similar. Use this to estimate an honest time, then, if you want to follow a pacer, use the next slower one than your estimate. eg if your honest estimate is 4:05 then start with the 4:15 group. This will tend to correct the typical error of going out too fast that even elites make sometimes. In the last third you can speed up if you find you have banked energy to burn.