Regarding "in accordinate with Occam's Razor", you should not minimize assumptions — in fact, you should maximize them.
Occam's razor is not about assumptions, but 'entities'; e.g. the quote
Entities are not to be multiplied without necessity. Source: Wikipedia
The point of the Razor is about having too many degrees of freedom — if your theory has a lot of flexibility to accommodate observation, then we haven't really learned much if you make observations consistent with the theory.
If we have the alternative, a theory that is inflexible and can only accommodate a narrow range of observations, then we learn a great deal when the theory consistently agrees with observation!
Given a theory, adding an additional axiom can only decrease the number of results consistent with the theory! The only effect an axiom can have is to let you prove new statements — and that means the negations of those statements are no longer consistent with the theory!
There is an obfuscating factor here, though; for some reason things are often discussed in the opposite direction.
For example, consider passing from the description of 3-space via Euclidean geometry to a description via a general Riemannian manifold.
In this comparison, Euclidean geometry is obtained by adding the additional assumption "the metric tensor is given by this specific formula". However, for some reason, this comparison would more often be phrased in the opposite direction: that Riemannian manifolds are obtained by adding the assumption "suppose the metric tensor is not given by the standard formula".
Passing to the Riemannian manifold description of 3-space has definitely multiplied entities, but it has reduced the amount of assumption you have to make about the nature of 3-space.