Let me restate to see if I understand:

It sounds like you're asking if you can use SSIS to take data from your source and transform/convert it into a flat file. This flat file is then used as a datasource by a SSRS report.

If that is what you're asking, then you should be able to. The limitation would be the SSRS connection types. So you may want to have your SSIS write out to a .xml file which the SSRS report can use for its data source.

HTH,

Rob