Although it is the cleanest way to do it, you do not need to use LabVIEW classes to make an updateable application. The real need is modularization. You need to ship more than one file. This will negatively impact your load time, but that may or may not be an issue, depending upon how you do it. The more you break up your code into multiple files, the more fine grained your update process can be. Currently you are shipping an EXE. If you change this to shipping an EXE and four packed libraries or LLBs, you have made incremental updates easier. The packed libraries/LLBs could contain VIs whose block diagrams and front panels are stripped, making them as secure as the EXE. Each file can be versioned and installed as a separate part, making incremental upgrades much easier.
All of this is made easier with LabVIEW classes, but they are not necessary. With a plug-in application I wrote in LabVIEW 8.0, we estimated about 30% more code due to not using LabVIEW classes (they came out in LabVIEW 8.2). It may be easier to modularize an old piece of code without classes than to convert it to a class-based architecture. I would certainly recommend new code use classes.
Good luck!
