Making a prototype into an end-user product

Now I am making Nanaju (see recent posts' photos) prototype into an end-user product.

P2PPCB wiring is good for prototyping but too costly and cumbersome for mass production or DIY kit. I'd like to make the assemlby cost cheaper at the sacrifice of huge initial cost. So I am designing this flex PCBA:

"ツメ" areas don't seem to have any function. They have, of course. BTW in Japanese "ツメ" means a craw or ratchet in this context.

The PCBA mates with this cavity of a frame:

Insert the PCBA vertically:

And slide the PCBA upward:

Now they mates tightly. No need to worry about slipping. The "ツメ" works like this:

This side of the frame mates with a key switch:

Complete:

No tools, no hand soldering. Easy and fast. Ideal for mass production and DIY kit. But hard to design :-) The initial manufacturing cost is expensive too.