(a) If the commissioner considers it necessary or appropriate in the public interest or for the protection of investors, the commissioner by rule may define:
(1) "equity security" to include a security that is similar in nature to an equity security; and
(2) "exempt security" for purposes of this chapter.
(b) In adopting a rule under Subsection (a)(2), the commissioner may define the term conditionally, on specified terms, or for a stated period.