Just run head first into the same question - client supplies 38k user details whats the probability that there are more than one or two duplicates user names here !!!
Question is do you update the svySecurity module and make it non standard hence miss out on future updates or scrap it all together and grow your own sub optimal version ?
This is really frustrating because svySecurity is a great enhancement to Servoy and a massive time saver however its effectively compromised by not using what surely is a standard approach to data record keeping ie unique ID