Hello and thank you for posting this challenge!
This is my first project as a freelancer on this website so please don't mind my rank.
Here are my solutions to your query:
1. I can provide proper boot config files via email so you can place them on usb stick and boot both x32 and x64 versions (not really ok since you might want to try other linux flavors, not just lubuntu).
2. easy step-by-step guide on how to create/add unlimited unix/linux/ubuntu/centos/debian etc flavors to your USB stick and boot them on the fly (via boot menu) without having to modify configs.
I personally had the same dilemma sometime ago so the solution you are asking for is within my grasp, implemented and tested: both x32&x64 lubuntus are booting up fine from my USB stick. If something goes wrong, I will also troubleshoot the issues you are experiencing at your end and will ask further questions in order to fix them/adapt to your current environment/platform.
I can send you friendly materials (screenshots, movies taken off my tests) via email or other way of file transfer facility, that reflect the functionality as per your requirements in this project.
Please do let me know if you require further clarifications on my methodology.
Thank you,
Dragos Ciobanu
Newbie freelancer UNIX administrator