Hero999
Shorted-gate TRIAC's have built-in Gate-MT1 shunt resistances approx. 33- ohm, but a 1Meg resistor would be outrageously high anyway for almost anything, a value <1K for non-Sensitive Gate TRIACs>1K for Sensitive Gate TRIACS.
This is not a Sensitive Gate type of TRIAC. BTA16-600B
For a single TRIAC to trigger your circuit may be practical for Sensitive Gate TRIACS, but as the OP said, many things to control, then this trigger circuit has to duplicated for each TRIAC to trigger, making a fixed power supply (Cellphone P/S) attractive.
You would need to trigger the TRIACs continuously if the MCU didn't have a fixed zero-cross reference for phase firing of the TRIACs, otherwise the results will be unexpected, chaotic, on-the-blink.