My concern would be that a court would find there is no patentable weight to "none or more". If you have a group of options (i.e. "the system of claim 1, wherein one or more of A, B, C or D is present"), it is easier to infringe (since you have four options), but it is also much easier to invalidate (because if there is prior art for A, B, C OR D, you have an invalid claim). By adding "none", even if A, B, C and D are all novel and not obvious, your claim doesn't require any of them, so if the independent claim is invalid, the dependent claim has no patentable weight that would provide a basis for validity. Basically, your dependent claim with "none" as an option can be interpreted as "you can do exactly what claim 1 says, or you can add A, B, C or D". Of course, your dependent claim is slightly different because it requires a new element (B), but everything after that doesn't help you as much as it should. The suggestion of breaking it out into two dependent claims was a good one.
- A method for doing A.
- The method of claim 1, wherein A comprises B.
- The method of claim 3, wherein A further comprises one or more of: C, D, E, and/or F
To see why the "none" option doesn't help, here is what that would look like if you wrote it as its own independent claim:
- The method of claim 2, wherein nothing further is added.
There is literally no patentable weight to claim 4. It rises and falls with claim 2.