I wrote a small story where Polish agents travel back to 1936 and launch a pre-emptive strike against Germany in early 1939. It's on this site search "Polandwank"
Found it by searching through your thread starts:
https://www.alternatehistory.com/discussion/showthread.php?t=126513
I feel it needed more planning and research. Given a 1936 start, an ISOT'd advisor would have little opportunity to revamp Polish industry to the point of overtaking Germany.
The discussion on this thread looks at some options (including my own view about joining and supporting the Little Entente)
https://www.alternatehistory.com/discussion/showthread.php?p=3002670
Skoda SIIc/T21
CKD V-8-H
Czech tanks could be advanced to a reasonable level by 1938, but a Polish advisor would be likely to warn the Czechs before then to deal with the Sudeten German agitators. Compulsory purchase and expulsion to Germany might make Czechoslovakia seem undemocratic and harsh on dissidence, but it would shore up the border against the Nazi fifth column. The ZB30 (the original Bren gun) was made in Yugoslavia and Romania as well as it's Czech homeland. Then there is the classic BESA medium machine gun.
A Mosquito and Hurricane design revamped with bubble canopy, laminar flow wings, armoured seats, Meredith effect exhaust and 4x 20mm cannons would be possible to build given detailed designs. Due to their wooden structures they would be less demanding for a rapidly expanding industry. The Little Entente offers four times the number of aircraft factories to build them in. Poland has some excellent pilots to make full use of them.
An 'alliance' Yugoslav Hurricane:
Rumanian made ammo/fuel/recovery tractor and trailer to a French design:
Able to tow a 47mm AT gun or greater instead of the trailer. These tractors allow rapid refuel and resupply of tanks to multiply their capability. Capacity of 350kg plus 600kg (trailer).
The Polish
TKS could be refitted earlier as 47mm SP gun, 37mm tank destroyer and 20mm gun scout tankette. Mortars are easy to mass produce in 60mm, 90mm and 120mm sizes. Bazookas are an old classic of ISOTs. The 'Ma Deuce' is hard to improve on for a heavy machine gun.
As I said in the other thread, logistics and communications are going to make the Eastern Europeans more useful in the field. Radios and code bombs will stop the Axis before they start. Cede Upper Silesia and East Prussia at the peace table.