I\'m with the idea that these classifications should be role, not by mass.
You could have a Bucket class that is 94732 blocks of dirt with no weaponry. I\'d hardly call it a Dreadnought.
I have Cruiser designs that are Frigate sized. Packed with turrets, shields and thrusters but hardly anything else - they\'re able to be small because everything is placed with efficiency, purpose, and compactness in mind. The smaller I can make it, the less thrust it needs to move, and the less hull I need to protect it, which also makes for a lighter ship. Something like 90% actual purpose and only 10% aesthetic.