A Redhill to Zones 2 to 6 annual travelcard would be £2556 and would be valid for travel to West Brompton or Imperial Wharf, if either of those are convenient for your base, but would require you to change at Clapham Junction (or at East Croydon onto or off a Southern train to/from Milton Keynes), and wouldn't be valid for Victoria or anywhere else in Zone 1, except that it would be valid on a bus in any of Zones 1 to 6. It would save £700 compared with an All Zones travelcard.
With Oyster, a Zone 1 single is currently £2.10. So the question would be whether you are likely to make more than 333 single Zone 1 tube journeys in the year (or something less than 333 if there is a price increase in January).
Also, this suggestion probably won't appeal if you are likely to want to do Redhill-Victoria or Victoria-Redhill journeys because of starting or ending your working day not at your Fulham base but somewhere in Zone 1 instead (as there would be the necessity of having to leap off at Clapham Junction to touch in or out).
