HW Modifications

Attaching sensors

All available ESP8266 GPIOs are used here. You can theoretically use RX, TX and GPIO0 for your own purpose, keep in mind that using RX and GPIO0 will prevent the device from booting up so you need to boot first before connecting anything to these pins. TX should be safe but it's dumping serial data during bootup so take that into account. If you really need a GPIO, that's not being used internally during boot you can solder GPIO5 (connected to status LED).

Adding IR blaster

This is NOT IR remote, but with skilled soldering, you can replace status LED (GPIO5) with side-positioned smd IR LED. The functional range of such IR blaster is questionable but status led is positioned rather conveniently for that.
You will also have to print custom enclosure with a hole at the front for IR blaster.