There shouldn't really be any problem with setting up a package that gets its source and runs from a specific network location, as long as you have the permissions set up correctly on the software folder. You'll be losing some of the benefits of using the Distribution Points and being able to pre-cache installs on clients, etc, but there's no reason it shouldn't work.
To create your new package:
- Right-click on Packages (or the sub-folder under Packages that this job is to go into),
- Select New -> Package, fill out the required details on the first page of the wizard (only the name is mandatory, but it's advisable to fill in more fields),
- On the Data Source page, don't tick the "This Package contains source files" box,
Then step through the rest of the wizard accepting the defaults.
Then in your newly created package right-click Programs, and select New -> Program,
- Give it a name and in the command line put your install command line, including the full path to the share and any necessary switches,
- Select any necessary options for the program in the rest of the wizard (leave Drive Mode on the Environment page at "Runs with UNC name").
Your program should now run directly from the specified source location. You just need to create an Advertisement that you can point at a Collection to distribute it.