It seems I am in the minority. I don't like being able to keep past ships. Move on, grow, evolve. Certainly breaks immersion and makes little game sense. Seems silly, like you have entire ships in your pocket, what happens to the crew compliment of a Sovereign class ship when you magically switch back to your tier one ship for a specific mission? Been following STO for a long time, sounds like they are going the video game route, not the MMORPG route. Dissapointing to me.
Just pretend you're playing through a flashback.
Honestly, though? This is excellent. It means I can advance as quickly as I want and still go back to gaming with my lower tier friends without being over-powered. That's nice!