For me portfolio has three parts:
1. the showcase you take with you, maybe during the rest of your life: documents in that portfolio must have electronic seals on it. For Universities it could be interesting to offer their students (also after graduation) some portfolio facilities to stay in touch with them and selling them this way extra courses after their graduation:
I am now looking at http://theospi.org/ for this purpose.
Moodle then needs an export function to that personal archive.
2. From the perspectiv of an Institute you offer a student a set of courses, ending up in certificates: for this purpose you need a catalog with descriptions of certificates and the set of courses you need for each certificate. Also the administration must be kept in a secure place: Should be part of the secure administration of the institute: based on the outcomes of this system you setup your Moodles. Automatic connection? not yet needed...
3. Having Moodle you can coach a student very good during a course and I do not see the need for a separate portfolio-system.
We could consider to use Will's bookmarks as a portfolio-option:
It sets bookmarks on a super-Moodle-level: you have them with you in all your Moodles...
Normally a student does all the exercises during a course. Nothing wrong with that, but if that student wants to candidate an exercise for his portfolio, he sets a bookmark and sends an email to his teacher (must be buid-in) The teacher gives this exercise an extra look and advises the student what to do if he wants to place it in his portfolio. (At the end of that course it must be improved.) This way you do not need that extra board of wise men that looks at your protfolio, long after you finished that product...
Creating a showcase-window in the personal page of each student? why not.. until he graduates? and then?