Today it might seem to be an hypothetical question. I read that Surveyor mission confirmed "re-igniting" a LOX+LH2 engine in space is successful. What if the use of H2 was not successful ? - specially re-igniting in space - !! Further, use of hypergolic propellants in LEM ascent module, was selected to ensure lift off from moon surface, which was verified during Apollo 10. Had that been unsuccessful, was NASA prepared to launch all Apollos with LOX+RP1 (or any other, PROVEN propellant configuration) configuration on all stages?
Using RP-1 and LOX for the Service Module and the LM was impossible.
Replacing the fuel by a less energetic combination would require larger tanks and different engines designed for another propellant and more thrust for the heavier SM and LM.
A heavier LM and SM would require another much bigger Saturn V, with larger tanks and more engines. Eight or even ten engines instead of five for the first and second stage.
So only the CM could be used, but another and totally different version of the SM, the LM and the Saturn V would be needed.
But LOX could not be stored in the SM and CM for more than a week between launch and splashdown.
If the Surveyor flights had failed to re-ignite the Centaur's RL10, the engine would have been redesigned until it could re-ignite.
While it was theoretically possible to build a moon rocket with kerosene instead of hydrogen upper stages (like the USSR's N1 program), the US had decided early on that hydrogen was more practical for upper stages leaving LEO. In fact, Von Braun favored kerosene for the Saturn family, but his colleague Krafft Ehricke, working at Convair/General Dynamics in the mid-50s, led the push for a hydrogen engine for the Centaur upper stage.
There are lots of things on spacecraft that are built redundantly. Some are even built to have dissimilar redundancy such as redundant sensors that measure the same thing but are built by different manufacturers. Another example is that some spacecraft have a backup flight software system written by a group of developers who are firewalled from the developers who write the primary flight software system.
There are however some things in spacecraft that have zero redundancy, and others that do not use dissimilar redundancy. The Apollo return capsule itself had zero redundancy. A backup return capsule was not launched in case the first capsule failed.
Propulsion systems oftentimes employ some form of redundancy. Some vehicles have multiple cross-fed propellant tanks, but all hold the same fuel or oxidizer. Some vehicles have redundant thrusters, but all thrusters are designed to use the same propellant. I have yet to see a vehicle that uses dissimilar redundancy in its propulsion system. The mass penalty for dissimilar redundancy in a propulsion system would be huge.
There are many problems with your suggestion.
The exact hypergolic combination (Aerozine 50 and nitrogen tetroxide) used by Apollo was already used and proven during Gemini. There was no concern that it would fail. (That was a major purpose of the Gemini program: to prove the technologies needed for Apollo.)
The specific impulse of the RP-1 S-IC first stage was 263 seconds; of the hydrolox S-IVB third stage was 421 seconds; and of the hypergolic CM and LM were about 310 seconds. You are replacing each propellant with an inferior one.
Your question seems to suggest using RP-1 for the Apollo third stage, CSM, or LM. By the time these parts of the spacecraft are used, the first stage -- which is the only stage that used RP-1 -- has already been discarded. So you would either need to keep the dead weight of the first stage with you, or add extra tankage to these later spacecraft components.
You can't just put RP-1 into a hydrolox or hypergolic engine and expect it to work; they are very different designs. So you would need to add additional engines to the third stage, CSM, or LM.
RP-1 is one of the dirtiest-burning rocket fuels, and can leave deposits in the engine. This makes it extremely unreliable to restart an engine. In contrast, hydrolox and hypergolic engines burn cleanly, and in the case of Apollo were used for re-ignitable engines.
Items #2 through #4 each imply adding extra weight and extra cost, for something that is less reliable than what was already used.