Well, if you apply for FLR after your marriage, then, yes, I would assume you could change jobs at will, because your ability to work would be tied to being married to a UK citizen, not the Work Permit.
As an aside, I don't think it would hold up any intentions of citizenship you might have.
Example:
A. Enter May 2003 on WP - eligible for ILR May 2007 - eligible to apply for citizenship May 2008.
B. Enter May 2003 on WP. Marry in May 2006, apply for FLR. Obtain ILR in May 2008, and eligible for citizenship immediately upon receipt of ILR.
There is a one-year requirement to have had ILR if you are applying on any other basis other than marriage. However, if you are applying for citizenship based on marriage, then there is no time requirement - you simply have to have ILR (and satisfy the residency requirements).
You will, however, be putting off getting ILR one year if you do it based on marriage rather than your WP.
I'm very happy to be corrected if I'm wrong on this.