My knife blocks are full of loads of bits of tubular ?nylon welded together at the base and in a ?nylon?plastic frame. The whole thing takes apart for washing and the knives push down among the plastic "noodles"
Agree about not using knife blocks - accidentally replacing an unwashed knife in the block would mean the gunge would be there forever. (Haven't come across Woofer's dis-assembly type). As to wall space, nothing to stop you attaching a suitably sized magnetic strip to the inside of one (or more, Eccles!) of the wall-cupboard doors. I've done this, and the magnetic strip is quite stong enough to hold the knives firmly when opening and closing the cupboard door.