OK, I wasn't sure if it's OK to do the install before AppSearch. And after your feedback I do remember that it has to be before LaunchConditions as you referred in your original question. This means that it has to be UI sequence as other stages are too late. Thus if you stick to the simplified-botstrapper approach you will have to force user to run msi with UI.
If it's not acceptable then you will have to go with the real bootstrapper (Burn), the one that is officially integrated with WiX (samples are included). Though WiX Burn has a reported bug that prevents this butstrupper from displaying EmbeddedUI. thus you will need to use either standard or custom bootstrapper UI (WinForms and WPF samples are also included).
If it's not acceptable then you will have to go with the real bootstrapper (Burn), the one that is officially integrated with WiX (samples are included). Though WiX Burn has a reported bug that prevents this butstrupper from displaying EmbeddedUI. thus you will need to use either standard or custom bootstrapper UI (WinForms and WPF samples are also included).