I have developed an SCR mains voltage regulator using AVR. PSU was derived from the mains voltage without any transformer or opto.
Mains synchronization is directly to an input pin of AVR using 3 meg. resistor.
Output pin of AVR fires an SCR using only one transistor and resistor. It has also RF remote control and runs OK.

The RF problem is, as mentioned before at the load side so a filter with and inductor and 2 capacitors is used to surpress RF. Because of an intelligent firing, regulator can also be used with inductive load (cos fi up to 0.1).

The problem is not micro power supply, any filtered and stabilized would do. Also zero switching is not a problem, I use a variable firing delay to regulate the output voltage.

Output filter at the SCR is the most important part of the design.