Usually we suggest users to create a PST+PLC (i.e. Persistent + Prelogon) profile when they want seamless network connectivity without any breaks. This can be done when creating a profile thru ITAdmin tool and by selecting both the options on the first page of ProfileWizard tool.
But this option works fine only with 802.1x profiles i.e. any profile with EAP.
Therefore, in your scenario since you are using WEP...it would not work.
You can try below option out and see if it works for your scenario.
1)Create one Persistent profile using WEP.
2)Create another Prelogon profile also using WEP and same SSID.
This will make your machine remain connected to network when nobody is logged on. But when a user will try to logon...there Proset will try to make a connection with Prelogon profile and break the exisitng connection with Persistent profile. User will experience a moment without network connectivity though