How expandable is the GPIO pin set for CM4? What good accesories and connectors are out there?

J3 - 40 pin FPC header

GPIO 0 - 27
all clockwork cards us pins 0-5, and 8-11 to control the power, headphones, backlight, etc.
the remainder of these pins, 6-7 and 12-27 are not connected on the CM4 module.

MINI_PCIE - Ext Module

GPIO 28 - 45, Camera Pins, 2x USB, Speaker L/R
all of these pins are connected to the CM4 and A06, but using them requires a custom ext module board that will expose them.

Note these pin numbers are the common clockworkpi notation, they don’t map 1:1 with the CM4 pins.
I made a table yesterday, but haven’t double checked it yet, the numbers i mention above are the SODIMM GPIO numbers.

Pin/GPIO #
CM4 SODIMM Connection Purpose
2 2 PMU_IRQ Power
3 3 WL_REG_ON Unused, to keep Wifi module off
4 4 WL_HOST_WAKE Unused, to keep Wifi module off
5 5 BT_REG_ON Unused, to keep BT module off
6 38 EXT MOD
7 39 EXT MOD
8 8 LCD_RESET Display
9 9 BL_CTRL Display
10 10 HP_DET Audio
11 11 PA_EN Audio
12 12 AUD_PWM0 Audio
13 13 AUD_PWM1 Audio
14 32 EXT MOD
15 33 EXT MOD 4g Module, RESET_MCU
16 40 EXT MOD
17 41 EXT MOD
18 28 EXT MOD
19 29 EXT MOD
20 30 EXT MOD
21 31 EXT MOD
22 IGPIO0 PWR_ON Power
24 34 EXT MOD 4G Module, POWER_MCU
25 35 EXT MOD
26 36 EXT MOD
27 37 EXT MOD
28 43 EXT MOD
CAM_GPIO 42 EXT MOD
ID_SC 1 PMU_SCK Power
ID_SD 0 PMU_SDA Power
SCL0 45 EXT MOD
SDA0 44 EXT MOD
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