vSZ documentation has code example for Wispr portal, including details of manipulations of user access.
I am not awear about any WISPR portal embedded in the vSZ. Actually, as much as I know there is no such thing (at least in v. 5.2). There is the guest portal, but it is quit different thing.
As there are a lot of developed WISPR portals are available, writing another one doesn't make very much sense, from practical point of view it would be better to use and customize some standard solution, which is supported and is under constant development.
Different case, if you do it as hobby, or to learn technology, than it is very much justified. Otherwise using, for example, Packetfence makes more sense.