The simplified turn-key experience you describe is precisely how AppInsight for Exchange has been designed for WMI managed nodes. It should be as simple as List Resources and check Appinsight for Exchange to enable. Click on AppInsight for Exchange from the All Applications tree, and if WinRM isn't configured you will be prompted to configure the server. Click "Configure Server" and you're done. Since Windows 2012 R2 will be the last version of Windows to support SNMP, our emphasis has been to improve the experience of application monitoring using Microsoft's recommended protocols as our first priority. Since AppInsight for Exchange leverages WMI to collect some information anyway, polling node CPU/Memory/etc. information made more sense than mixing three different polling methods for a single host. (SNMP/WMI/WinRM).
If you would like to experience the slipstreamed configuration process included as part of AppInsight for Exchange first hand while continuing to poll the node via SNMP, I suggest changing the node polling method to WMI, enable AppInsight for Exchange, then switch the node polling method back to SNMP.