Crossover operator in genetic algorithms in Neural Networks
I don't think you should.

But, supposing the structure is the same in all individuals, you could take a random set of nodes from one, and the rest from the other, and just keep all out edges from nodes you selected.

Another alternative is taking a random set of edges from one, and the rest from the other.

A third alternative is to take the first $\ell$ layers from the first individual and the last $L-\ell$ layers from the second individual.

As you can see, there are very many approaches, and I don't think any of them will be satisfactory, but I hope you try and see for yourself.