Lightness and cheapness should frankly only be "bonus" characteristics when it comes to bass gear. Anybody who wanted an instrument with featherlight gear should have taken up the piccolo. The door is over there, you can see yourself out.
Physics is a cruel mistress. I know it sucks that Johnny Guitar can plug into a 12w Champ with an 8 inch speaker from 50 years ago and make your ears bleed, but bass just doesn't work that way. You need a certain amount of size and weight to get "the tone". Certainly technology has come a long way, and the band I ran sound for the other day in a park, the guy just had a 250W TCE head and a GB 1x12 and it sounded full and nice, but this was a super tight pro level top 40 band where everyone knew what they were doing and subtlety and taste were the main targets. In a metal band, you just need cone area. There's simply no way around it. Really, if you're in a metal band and your bass rig weighs less than 100 pounds and you actually have enough volume with a tone that is stylistically appropriate, you're doing pretty good.