(Derek Davis/Staff Photographer)PORTLAND — City officials reacted with a mixture of excitement and caution Tuesday regarding the plan by the Portland Hearts of Pine to build a $50 million soccer stadium off the western edge of Commercial Street. Advertisement“I’m excited for the possibilities we can imagine now for Cassidy Point,” said Councilor Ben Grant. A rendering of the proposed new Hearts of Pine stadium, left, and the Cassidy Point Pier in Portland. On Tuesday morning, attendees at the Cassidy Point event sat about 50 feet from the coal pile, drinking cans of sparkling water while music played over speakers. But, beyond that, said the Hearts of Pine’s current home at Fitzpatrick Stadium has not been large enough to meet the overwhelming demand for tickets.