It sounds like your decision process is similar to mine... the other car in my garage is a Porsche 911 - not quite a Lotus - but lightweight, sharp, agile (rear-wheel steer), super tractable and forgiving in terms of what you can get away with adjusting the car going round a corner. All the things folks like about the 4BW.
The question I asked myself is why I would want a second car as a fun daily that prioritizes doing the same thing as the 911, but slightly worse? With the 5BW I get a completely different driving experience for either road or track - and variety is the spice of life.
I do think the 4BW would be an amazing one car solution or an amazing fun daily/canyon carver when paired with a more pedestrian family car. But if you already have a Lotus, it's not going to beat a lotus on handling and feel.