Small Business Regulatory Flexibility Improvements Act This bill modifies the rulemaking requirements and procedures of federal agencies under the Regulatory Flexibility Act of 1980 and the Small Business Regulatory Enforcement Fairness Act of 1996, including how agencies consider economic impact with respect to small entities. Specifically, the bill requires agencies to consider the direct, and the reasonably foreseeable indirect, economic effect of a rule on small entities when determining whether a rule is likely to have a significant economic impact. Further, the regulatory flexibility analysis for rules with a significant economic impact must include a detailed description of alternatives to a proposed rule that minimize any adverse significant economic impact or maximize any beneficial significant economic impact on small entities. The bill also expands the types of agency actions (e.g., revisions to land management plans) that are subject to a regulatory impact analysis. The bill removes the authority for an agency to waive the regulatory flexibility analysis requirements and requires the Office of Advocacy of the Small Business Administration to issue rules for compliance with such requirements. The bill also modifies the procedures for the (1) gathering of comments for a proposed rule, (2) periodic review of agency rules, and (3) judicial review of final rules.