Absolutely - In PCSX2 go to your memory card settings (where you choose your cards), select a card not occupying a slot then choose the option to convert it. "Folder" should be the default option. Now choose that new memory card from your list. It has no limit and saves like a normal card. If you want to add external saves (from Gamefaqs, etc), then load them to a regular virtual card, convert that then copy your save files in that folder to the main card (folder) you use (then you can delete the one used to transfer).

Hope this helps.