Initiative dates are auto-set based on linked release dates to allow for the most direct timing relationship. We would suggest linking releases to initiatives (based on your features) to enable you to leverage the auto-set.
At this time, based on current priorities and community feedback, we are unlikely to make updates in this area. We hope you can understand.
I would agree with this request. We currently have product initiatives that are being delivered on across several releases, and it would be great if there were some automated way for the initiative start and end dates to be based on the date of the first feature that is shipped for this initiative, and the date of the latest release date for the features that are linked to the initiative.