Mexico had a few airplanes before WWII, including some license built.

In 1929 Mexico bought 12 Vought O2U-2M (M for Mexico Export) from the US.
They then license built 31 of O2U-4A's
In 1937 they then purchased from Vought 17 more, V-99M (Vought Model, M-Mexico export)

Several other countries bought the O2U (variants) leading up to 1936; to include but not limited to: Brazil, Peru, Argentina, China.
https://en.wikipedia.org/wiki/Vought_O2U_Corsair

It was a Observation Plane, equipped with 1-2 .30cal MG, bombs, and a trainable rear MG.

Here is a good equipment variant to add to MEX (or USA or other) history file:

create_equipment_variant = {
name = "O2U-4A" # O2U-2M or V-99M
type = small_plane_cas_airframe_0
modules = {
fixed_main_weapon_slot = bomb_locks
fixed_auxiliary_weapon_slot_1 = light_mg_1x
engine_type_slot = radial_engine_1_1x
special_type_slot_1 = lmg_defense_gunner
fixed_wing_slot = biplane_wing
}
icon = "GFX_USA_LAMP_o2u_2"

It is a copy/mod of the O2U alreadly in the US history. There is no ingame difference between the models due to the available technologies

For the BBA file:

air_wings = {
277 = {
small_plane_cas_airframe_0 = {
owner = "MEX"
amount = 12
creator = "USA"
version_name = "O2U-2M"
}
small_plane_cas_airframe_0 = {
owner = "MEX"
amount = 31
creator = "MEX"
version_name = "O2U-4A"
}
small_plane_cas_airframe_0 = {
owner = "MEX"
amount = 10
creator = "USA"
version_name = "V-99M"
}
}
}

This is if the US has the above-above added equipment renamed. These are CAS as at the time they were use to support ground troops, and didnt really have other planes to dogfight. Also MEX, USA, and other countries dont have Photo Recon researched in 1936, so it was not added.

While MEX may not have had all 53 aircraft at the start of 1936 (being built - V-99M, or operational due to misc loss), it does make it slightly more historical; including the domestically built planes

Please consider these additions to your mod.

Thank you