I played with 1942.2 using TcB and Mech.
I can just suggest to not add more units.
Just changing some Inf into Mech and some Fg into TcB.
For example: you add UK TcB in SZ 35, there is already a Fg. Just change it for a TcB so the Carrier still only have 1 plane on board.
Adding a second one is very unbalancing against Japan Carrier in SZ 37, since it is on of UK’s opening attack (granting an additional unit will make Japanese carrier a piece of cake).
Just upgrade 1 Fg in SZ35 and SZ37.
For UK, I will upgrade one Fg to a TcB on England. So it will be a +2 IPCs change.
For JAPAN, upgrade the Fg on Japan to TcB. So it will be a +2 IPCs change.
For USA, I will prefer to change the Hawaiian Fg for a TcB instead of the one on board Carrier since Japan can directly destroy the carrier in SZ 52, Fg is better on defense let’s make it pay Japan if they attack Pearl Harbour and keep the TcB on the island for counter-attack with the Fg from US West Coast. +1 IPCs change
For GERMANY, upgrade either Balkans Fg or Eastern Europe Fg (don’t add any) Germany has enough planes. And put another one on the Northern West coast of Europe or Norway, ready to attack Atlantic SZs. +2 IPCs change.
For RUSSIA, I wouldn’t add a TcB in Russia, just change the Fg for a TcB. A +1 IPC change.
So to summarize up grade Fg to TcB:
Russia convert 1 Fg in TcB,
Germany, get 2 TcB from 2 Fg,
UK get 2 TcB,
Japan get 2 TcB,
USA get 1 TcB.
So Allies had 4 TcBs and Axis had also 4 TcBs.
Just some 8 minor changes.
For Mech, I would only change 4 Inf into 4 Mech for each side.
Germany get 3 Mechs and Japan 1 Mech.
Russia get 2 Mech, Uk get 1 and USA get 1.
I think UK should also get 1 Mech, maybe in South Africa (it could be useful, if not plausible).
In this way, Axis gain + 8 IPCs and Allies also.