Remove subscription delay for existing/past members. Charge them the full level price immediately at checkout. Update the level cost text.

my_pmpro_remove_subscription_delay_for_renewals.php

<?php
/**
 * Remove subscription delay for existing/past members.
 */
function my_pmpro_remove_subscription_delay_for_renewals() {
	if ( is_admin() || ! is_user_logged_in() ) {
		return;
	}

	$order = new MemberOrder();
	$lastorder = $order->getLastMemberOrder( NULL, array( "success", "cancelled" ));

	// If user currently has a membership level or previously had a membership level, remove custom trial.
	if ( pmpro_hasMembershipLevel() || ! empty( $lastorder ) ) {
		remove_filter('pmpro_profile_start_date', 'pmprosd_pmpro_profile_start_date', 10, 2);
		remove_action('pmpro_after_checkout', 'pmprosd_pmpro_after_checkout');
		remove_filter('pmpro_next_payment', 'pmprosd_pmpro_next_payment', 10, 3);
		remove_filter('pmpro_level_cost_text', 'pmprosd_level_cost_text', 10, 2);
		remove_action('pmpro_save_discount_code_level', 'pmprosd_pmpro_save_discount_code_level', 10, 2);
	}
}
add_filter( 'init', 'my_pmpro_remove_subscription_delay_for_renewals') ;

// Filter the price on the levels page to remove one-time trial.
function my_pmpro_no_delay_for_renewals_pmpro_level_cost_text( $cost, $level ) {
	global $pmpro_pages;

	// Not logged in?
	if ( ! is_user_logged_in() ) {
		return $cost;
	}

	// Check the current user's order history.
	$order = new MemberOrder();
	$lastorder = $order->getLastMemberOrder( NULL, array( "success", "cancelled" ));
	
	// If the user already had the trial for this level, make initial payment = billing amount.
	if ( pmpro_hasMembershipLevel() || ! empty( $lastorder ) && is_page( $pmpro_pages[ 'checkout' ] ) ) {
		$cost = sprintf( __( '<strong>%1$s per %2$s</strong>.', 'paid-memberships-pro' ), pmpro_formatPrice( $level->billing_amount ), pmpro_translate_billing_period( $level->cycle_period ) );
	}

	return $cost;
}
add_filter( 'pmpro_level_cost_text', 'my_pmpro_no_delay_for_renewals_pmpro_level_cost_text', 25, 2 );

// Filter the price at checkout to charge the billing ammount immediately.
function my_pmpro_no_delay_for_renewals_pmpro_checkout_level( $level ) {
	global $discount_code;

	// Not logged in?
	if ( ! is_user_logged_in() ) {
		return $level;
	}

	// Not if using a discount code.
	if ( ! empty( $discount_code ) || ! empty( $_REQUEST[ 'discount_code' ] ) ) {
		return $level;
	}

	// Check the current user's order history.
	$order = new MemberOrder();
	$lastorder = $order->getLastMemberOrder( NULL, array( "success", "cancelled" ));

	// If the user already had the trial for this level, make initial payment = billing amount.
	if ( pmpro_hasMembershipLevel() || ! empty( $lastorder ) ) {
		$level->initial_payment = $level->billing_amount;
	}

	return $level;
}
add_filter( 'pmpro_checkout_level', 'my_pmpro_no_delay_for_renewals_pmpro_checkout_level', 5 );