Franck,
Yeah, that might be your only option. Don't forget that Visual Studio can generate GUIDs for you .
Your point about templates is a good one. I have previously submitted a request to have the behaviour changed: https://connect.microsoft.com/SQLServer/feedback/ViewFeedback.aspx?FeedbackID=277249
which I talked about here: http://blogs.conchango.com/jamiethomson/archive/2007/05/15/SSIS_3A00_-New-suggestion-for-templates-in-Katmai.aspx
-Jamie