Reset pulse generator for ESP8266
Using your basic idea, you can do something like this (just adding the one part, the circuit in the dashed box simulates what is on your dev board): 







simulate this circuit &ndash; Schematic created using CircuitLab



The 2N7000 MOSFET is used to discharge the 100nF power-on reset capacitor on your board. 

The simulation shows power-up at t=0 and then the reset switch pressed and held at t = 100ms. 

Looks like you could easily go to 10nF and 10M resistors, and even less on the capacitance but take care of the MOSFET input capacitance if you try to go very low or try to substitute a different type of MOSFET (most of which will have much higher gate charge).