Maybe rewrite the feat to allowing a another attack everytime you hit with main hand, so say you had extra attack, you hit once with attack action, BA hit with other weapon, extra attack, then another other weapon attack. But still limit to light weapons, and you have to land the first attack to trigger a second attack?

Not sure what kind of problems something like this would create, but other options would include
-making twf more mobile
-making twf have a better defensive option
-a different way to make twf have more attacks or cost no BA.

Realistically we all know that twfing isn't very good, but this is fantasy so it should be good as anything else if not amazing. I don't play D&D to simulate reality, I play to be as bad*** as every twfer on screen (or book Entreri>Drizzt )