Java bytecode: No, that is too complicated work, and too hard to maintain. I will just use Java.
I don't quite know your meaning about "Java access" but if you means touch java class and invoke java function in wren vm, yes, there will be.
And after the migration I will add lots of new syntax in it.
For example, continue keyword in loop, include keyword in module management, interface in classes, and lots of other things.
But first, I will focus on the migration.
No doubt C is fastest, but develop in C really makes me feel sick.