Cannot use SharePoint feature to deploy content types using content type hub functionality when using XML elements

*** Update 11/05/11 ***
Over the last few weeks I have been contacted regarding this post and had contradicting reports that you are in fact able to create a feature to deploy content types to a content hub without the need for the feature to be enabled on each subscribing site collection.
My original issue experienced was also replicated by others once I’d posted this issue so this seems a strange one as since both of us are unable to recreate the issue.
Upon retesting the issue I can confirm that you are able to deploy a feature to a content type hub without the need to enable the feature on subscribing site collections.
Thanks to Chakkaradeep Chandran for following up on this and feeding back his findings.
*** Original Post ***
I’ve recently stumbled across a restriction of using the content type hub in SharePoint 2010 and I am a little surprised by its behaviour. From a quick search around there was very little discussing this so thought I’d post a blog on my findings.
So the plan was to leverage the new content type publishing feature in SharePoint 2010 alongside programmatically deploying site columns and content types using a feature to simplify deployments. Admins and developers of MOSS 2007 will recall that to deploy content types to multiple site collections easily required a feature creating with the necessary customisations. A downside to this was that every time you needed to update the content type you had to redeploy the feature with the updates.
An assumption on my part with the new SharePoint 2010 hub was that when you create a feature to deploy content types all you needed to do was to enable that feature on the content type hub and publish this out to subscribing site collections. Unfortunately it doesn't seem to work this way as subscribing site collections do not receive the published content types and looking at the error log on the receiving site collection states that it it requires the custom content type feature to be enabled which defeats the object as we will be back to the MOSS 2007 scenario mentioned above.
So some thoughts around options available to use to deploy content types to the content hub for successful publishing:

• Raise it with Microsoft
• Create a PowerShell script that can receive a maintainable XML input file to update the content types on the hub.
• Not sure if this is possible but if the feature could be enabled on the subscribing site collection and have a dependency on the ‘Content Type Hub’ feature before deploying the content types.

Thanks to Chris O’Brien for confirming this for me on Twitter. As always I welcome your comments / feedback / findings on this.
*** Update 30/11/2010 ***
After posting my blog entry a great SharePoint community member Nick Hadlee posted a comment with his initial thoughts / frustrations and kindly shared further finding’s based on a quick test he carried out.
So to explain further the way the feature I described above was deployed was using an XML file which requires no code.
Nick pointed out that if you created a code based deployment of the content types using a feature receiver this works. This is effectively the same as using the UI to enter content types / columns.
So to conclude there is a workaround to deploy content types using a feature however this requires coding rather than the XML format.
I did have a thought around enabling the feature on all site collections and then seeing if any updates from the Hub were published however I’m sure this will get messy in the long run as updates and changes are applied.
Credit to Nick Hadlee for his input and also my client who I’m currently working with who has helped in investigating this.
*** Update 10/01/2011 ***
Nick Hadlee has thankfully posted his workaround which can be found here. Again thanks Nick for following this up and hope its useful.