Writing this up to show what i think about this doctrine, as the one i've played for so long. All my ratings (5/5 being the highest) are my opinion of which abilities are better than others.
T1:Holding The Line - Nice T1, just a basic infantry buff helping them in cover slightly. Pretty balanced when comparing all similar T1s. 3/5
Mobile Reinforcements - Again a very good T1 since every tank comes in half the time. Maybe it shouldn't be all platoons with a vehicle, but all platoons with a Heavy tank (cromwell, CCT, Churchill, Firefly) since this could be slightly OP. 5/5
Desert Rats - Excellent little buff for armour, very good for RE, pretty balanced too. Just makes tanks better when standing still, very good against infantry 3/5
The Basics - Very useless T1, the worst of all the building T1s, even though i don't really fortify stuff myself, it's just not worth it. I suggest to add sappers building Tank Traps and thats fine, even if you take away Tommy infantry's ability to build Sandbags. 1/5
Improved Engines - Excellent for Churchills, noticable mostly on rollout and when driving on roads. Combined with Flanking manauvers this works really well, but remember it's only max speed so it won't be of use very often. 3/5
T2:Hull Down - Useless for most tanks i'd say. Immobilise in EIR is a massive disadvantage and i think it's quite useless, however this may become much better if T3s/T4s come in like Hull Down Command or something. Good buffs, but not useful 2/5
Petard Rounds - AVRE available, a fantastic investment, but you will need to get the T3 for it and also get it to Vet2 to make it deadly and feared. 3/5
Mk VI - OP right now, way too good, however it should stay as a T2. I suggest removing the Mine Flail upgrade for this churchill to balance it out a bit. A must have. 5/5.
Note: If you get MkVIs you don't really need to get Crocs, these things kill infantry pretty well with a CCT.
Ablative Armour - Not an amazing ability by the looks of it, but it works wonders when facing churchills against P4s/Schrecks. basically makes them much harder to penetrate. Duration is amazing as 45 seconds, i like the ability and would reccomend it. 3/5
Boys AT Rifle - I've never used this, not interested in a Light AT. I rely on 4 ATGs, Mk VIs as general AT and a Firefly especially for heavier tanks. This would probably be good against PE but i haven't used them so i'm not going to rate it.
T3:Flame Modifications - Fantastic T3, perfectly balanced. I couldn't say much more, even the vet is balanced. If you go MkVIs however you may not want this, and if you go AVRE don't get this either. 4/5.
Bogged down - A literally this is a button you can use on anyone in sight. Seems like it would be great against Panthers, Tigers, KTs and Jagds and actually give your Mk VIs a chance of doing serious damage, but either way i wouldn't consider it amazing as a T3 -33% moment speed just doesn't seem like enough to me either, i think -50% would balance the ability and make it more useful. 3/5
Bombardiers - Lovely buff to the AVRE very, very good. Balanced by the looks of it too. 3.5/5
TBA - I suggest that this should be Improved Emplacements, somewhere along the lines of "Emplacements get +25% health, +5 Range" The range buff would make it T3 worthy, and the health would help too. Right now the emplacement side of RE is non existant.
TBA - I suggest a possible general armour buff "improved armour", maybe all tanks recieve 15% less damage, just something easy, or maybe even something relating to the Kangaroo Carrier
T4:For King and Country - It's for the Fatherland, but its a T4?
?? I don't see it being amazing, i'm not even trying it for that reason. It's only defensive, and only in friendly territory. 2/5
Flanking Maneuvers - Great T4, well made and balanced too. Many buffs, the main one being speed. Works very well with staghounds rushing turreted defenses/paks 4/5
TBA - Possibly an Emplacement Buff again, a sort of "sim city" buff.
Many TBAs for T4s need to be filled