#Liverpudlian Accent - Calm down, calm down....
Using a bat with a rubber insert in it is clearly illegal and anyone else on the pitch will be able to see it.
Using a more traditional lam is also illegal.
I have used a traditional lam in nets and frankly, it didn't help me time the ball, and it didn't help me become a better batsman. The difference was when I hit the middle, and, it wasn't that big a difference, i.e., it might have turned a 3 into a 4 on a very good pitch. Was it the Lam or Gooch's skill that scored 333 at Lord's?
The point being
1. Lams do make a difference all be it very small
2. A rubber lam would make a bigger difference and be completely obvious.
3. Certain batmakers in the past have been warned about creating performance enhancing blades by the MCC...
4. It isn't illegal in the laws of cricket to make a laminated bat of any sort, or even an aluminium bat. It is, however, illegal to use one in a game of cricket.
Ergo, let them be made. It's always interesting to see something different.