Q: How to handle prerequisites for an .msix installer? We have a basic msi installer made by installshield. The purpose of the installer is to install a WPF application. This installer has a number of prerequisites, that are part of the installer .exe file and will be installed as a first step of the install if necessary. One of them is Sql Server Localdb. 
We're now looking at creating an .msix installer. We've made some progress using the visual studio project type called "Windows Application Packaging Project". The resulting .msixbundle file installs our program under Program File\WindowsApps.
Now comes the question of how to install the prerequisites that are necessary for our program to work. Is this possible using msix?

A: For this MSIX packages include support for dependencies. The operating system will automatically get those dependencies and install when your user installs the app.
As you can see from the MSFT docs, the dependencies include a reference to another msix/apps package. So what do you do if you need to install an application that is not packaged in this new format (a highly probable situation).
Microsoft published an update (that they say it should be used only by game devs) that indicates we could trigger the installation of an MSI/EXE from the main MSIX package that installs our app.
If you didn't noticed from my profile, I work in the Advanced Installer team. Here we are currently investigating this support to see if/how MSIX packages could bundle other older setups to create a "hybrid" distribution method.
[Update] Including Fred's comment from below. A sample on how to trigger an MSI from an MSIX package:
https://www.advancedinstaller.com/forums/viewtopic.php?f=7&t=41018#p110135
