Casillas joins Vicente del Bosque, Raúl González Blanco and Fernando Hierro — as Sunday's election gives members their first vote in twenty years.
Speaking to media ahead of the final public act before Saturday's official close of campaigning, Riquelme emphasised the historic nature of the moment.
"It is very important that the member, after 20 years, is going to be able to vote. It is an effort of so many people in terms of time — what we have done."
On the four legends who have committed publicly to his project, he was openly emotional.
"I want to give thanks above all for the courage of the four legends and captains of Real Madrid. They are truly people who love and seek the best for Real Madrid — and who would never allow anything bad to happen to Real Madrid while they are here."
Casillas, who won two Champions Leagues and four La Liga titles during his time at the club, joins Del Bosque, Hierro and Raúl in what Riquelme has framed as the authentic heart of the club's European peak — the figures associated with the seventh and eighth Copa de Europa triumphs.
On his basketball proposals, Riquelme called for the section to be given equal institutional standing.
"Basketball has made Real Madrid great for decades. We cannot treat it as a secondary section when it represents history, European prestige and the future for many members."
The candidate did not name his intended head coach, though he indicated that work on that front was continuing into the final hours of the campaign. His coaching announcement is expected on Saturday. Florentino Pérez, who pledged on Thursday to submit a €150m offer to a Champions League club on Tuesday, remains the strong favourite to win a seventh presidential term on Sunday.