Customers Performing Own Upgrades. How Hard Can It Be?

[timmers]

I want to design into future products the ability for a customer to connect their product to a PC and run a upgrade file which re-programmes the product.

Having looked at the bootloader method, I think that could work in principal, but trying to get the customer running the Microchip bootloader programme is too complicated.

Attached is my concept schematic (untested) showing how I could take over control of the serial port from the normal circuit.

The tricky part is getting a GUI to perform the actions automatically.
Is there anything I should be looking at before I commision a GUI be written. Also any suggestions on the circuit would be useful.

Thanks,
Tim.