You can't set up multiple datasources in Application.cfc to be used **implicitly** in your queries. The "this.datasource" can only be set to one datasource name. However, nothing is stopping you from storing a structure of datasource names in the application scope:
<cfset application.myDSNs = StructNew()>
<cfset application.myDSNs.DSN1 = "myDSN1">
<cfset application.myDSNs.DSN2 = "myDSN2">
...
Then in your query, you would do:
<cfquery name="qDoctype" datasource="#application.myDSNs.DSN1#">
...
HTH,
-Carl V.