jPortable w/FirefoxPortable conflicting with installed Java

I have users that require Java 6u26 to access an on-site server application. I've fought for years to get the server app updated to reduce security vulnerability, but apparently budget trumps best-practice every time.

A few days ago, some of these users found themselves unable to access an external website they need unless they update to a newer Java version. Inside, I'm clapping and cheering that this day is finally here, but on the outside, it falls on me to figure out a solution.

I was excited to discover portableapps.com and quickly imagined portable versions of Firefox & Java were the answer to my troubles. I could update all company computers with the latest Java, protecting us from their potentially unsafe browsing habits, while providing them an icon to click, only for accessing the local server's ancient app.

A little troubleshooting later, I've run into a snag and could really use some guidance on how things work behind the scenes. Let me start by saying I have set plugin.scan.plid.all to false in pFirefox's about:config page. And if I install pJava and pFirefox with no other Java installed on a (W8-64bit, if it matters) machine, everything works great. Surprisingly however, once regular Java is installed everything breaks. pFirefox Add-ons still correctly lists only 6u26 in Plugins, but pFirefox instantly turns "Not Responding" demanding a force-close when trying to run the local app, Oracle's Java version detection utilities, and other random Java websites I found searching for additional datapoints ie: http://javatester.org/.

I tried adding the pJava's bin path into the System Variables' Path field ahead of the regular Java entry. Then instead of pFirefox locking up, Java's website gives me an error message referencing the -installed- Java version instead of pJava. The local app opens to the home screen, but any further interaction with buttons/data is impossible. Javatester.org appears to run fine but shows the installed Java version instead of the pJava version. And running 'java -version' from a command prompt shows 6u26 like one would expect given the old version's higher path placement.

At this point, I know I need to head off pFirefox (or maybe pJava) from looking externally for Java settings instead relying only on itself, the way it did before I installed regular Java, but I have no idea how to go about doing that. If I uninstall regular Java, everything starts working fine again. If anyone has further suggestions, please let me know. Thank you!