You don't want to do that. The FIM Portal should be installed in its own instance of SharePoint (because you normally turn off Indexing of that SharePoint instance). That being the case there is no reason to use Enterprise unless you want to pay Microsoft
for the additional licenses to SharePoint Enterprise. Plus it is not officially supported.
From (http://technet.microsoft.com/en-us/library/jj863246(v=ws.10).aspx ) you can install FIM Portal on SPF 2013 if all of the four conditions are true:
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The SharePoint 2013 site collection is running in 2010 experience mode
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Server-side viewstate is to be disabled.
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Self-service upgrades on SharePoint Foundation 2013 from SharePoint 2010 experience mode to 2013 experience mode are not allowed
- Claims-based authentication is turned off