Article V rules how the constitution can be amended, provided that
... no Amendment which may be made prior to the Year One thousand eight hundred and eight shall in any Manner affect the first and fourth Clauses in the Ninth Section of the first Article; and that no State, without its Consent, shall be deprived of its equal Suffrage in the Senate.
Given these texts, it seems that the content of an amendment has some restrictions. However, if the legislators and the states want to amend one of these provided conditions, say equal Suffrage in the Senate, can't they just do two amendments, in which one amends article V itself followed by the Senate related amendment? In this sense, the threshold to amend the Senate rules is not really increased, despite a possibly longer amendment procedure.