Update of simple 2 layer PCB design and producing extended Gerber files (RS-274X)

As a thermal solar installer, I'm in need of an updated design of a delta-T controller with approx 20 components. The current design has some end-of-live components and I want an alarm (piezo buzzer) added to the layout as an option. The current PCB has been reversed engineered in China, so the circuit diagram, PCB layout and BOM will be provided (in a ancient Eagle version). The PIC or microprocessor used, is the ST6210/HWD. It's no longer in production, but I've got sufficient overstock available and can program the device myself. So out of scope for this project. At least 2 PCB switches and a crystal oscillator are nog longer in production. Availablity of every component needs to be checked for sourcing and production purposes for the next 10 years. On the PCB an audible alarm (piezo buzzer or so) is to be added as an option. The exact dimensions of the PCB are not to be changed, since it fits snugly in an existing enclosure with small tolerances. Output is a set of extended Gerber files (RS-274X) that is complete and ready for ordering a first batch by any modern PCB-manufacturer. The final milestone is proof that the Gerber is accepted by such a PCB-manufacturer (eg pcbgogo) without comments. Knock out criteria are proper experience and the ability to communicate in English (no Google translate user please!!). I tend to prefer a design made in Altium. But Fritzing, KiCAD and Eagle are also possible. Attached are BOM and some PCB pictures. More information will be provided.