Example of how to show different payment option levels at checkout with Paid Memberships Pro.

pmpro_level_groups.php

/*
	Show payment options (as levels) at checkout.
*/

// Define groups of levels. array(1,2) means that levels 1 and 2 are in a group and options will be shown for both levels at checkout for those levels.
global $pmpro_level_groups;
$pmpro_level_groups = array(array(1,2));

//show options at checkout
function pmprogl_pmpro_checkout_boxes()
{
	global $pmpro_level_groups, $pmpro_level, $discount_code, $wpdb;

	//no groups? return
	if(empty($pmpro_level_groups) || empty($pmpro_level))
		return;

	//get id for discount code
    if(!empty($discount_code))
    	$discount_code_id = $wpdb->get_var("SELECT id FROM $wpdb->pmpro_discount_codes WHERE code = '" . $discount_code . "' LIMIT 1");

	//get first group this level is in
	foreach($pmpro_level_groups as $group)
	{
		if(in_array($pmpro_level->id, $group))
		{
			//show options for these levels
			?>
			<table id="pmpro_level_options" class="pmpro_checkout top1em" width="100%" cellpadding="0" cellspacing="0" border="0">
			<thead>
				<tr>
					<th>Select a payment plan.</th>
				</tr>
			</thead>
			<tbody>
				<tr>
					<td>
						<div>
							<?php 
								foreach($group as $level_id)
								{
									$level = pmpro_getLevel($level_id);

									//apply discount code
								    if(!empty($discount_code))
								    {
									    $code_check = pmpro_checkDiscountCode($discount_code, $level_id, true);
									    if ($code_check[0] == false) {
									       //doesn't apply to this level
									    } else {
									        $sqlQuery = "SELECT l.id, cl.*, l.name, l.description, l.allow_signups FROM $wpdb->pmpro_discount_codes_levels cl LEFT JOIN $wpdb->pmpro_membership_levels l ON cl.level_id = l.id LEFT JOIN $wpdb->pmpro_discount_codes dc ON dc.id = cl.code_id WHERE dc.code = '" . $discount_code . "' AND cl.level_id = '" . (int)$level_id . "' LIMIT 1";
									        $level = $wpdb->get_row($sqlQuery);
									        //if the discount code doesn't adjust the level, let's just get the straight level
									        if (empty($level))
									            $level = $wpdb->get_row("SELECT * FROM $wpdb->pmpro_membership_levels WHERE id = '" . $level_id . "'");
									        //filter adjustments to the level
									        $level->code_id = $discount_code_id;
									        $level = apply_filters("pmpro_discount_code_level", $level, $discount_code_id);
									    }
									}

									//apply filters
									$level = apply_filters("pmpro_checkout_level", $level);

									?>
									<input type="radio" id="pmpro_level_<?php echo $level_id;?>" name="level" value="<?php echo $level_id;?>" <?php checked($pmpro_level->id, $level_id);?>>
									<label class="pmpro_normal" for="pmpro_level_<?php echo $level_id;?>" /><?php echo pmpro_getLevelCost($level, false, true);?></label>
									&nbsp;
									<?php
								}
							?>
						</div>
					</td>
				</tr>
			</tbody>
		</table>
			<?php
		}
	}
}
add_action('pmpro_checkout_boxes', 'pmprogl_pmpro_checkout_boxes');

My requirement for "payment options" on each specific membership level is, for example:

• Option-1: 12 installments of $35, on PayPal;
• Option-2: Single payment of $350, on PayPal;
• Option-3: Single payment of $350, on BankTransfer/Check.

Using "pmpro_level_groups.php" also does not attend that requirement, since:
(i) I have to create "multiple levels" anyway (there are no "options" on a single membership);
(ii) Outcome gets confused on which payment method should use, mixing PayPal and Check.

Needs improvement.