A short excerpt from the supertest patch notes for 9.14:
Simplified vehicle module research for beginners
To simplify the process of familiarising new players to the game, the research system for Tiers I and II has been changed. Tier I Vehicles will have just one module available for research - a gun. Tier II vehicles will get the opportunity to research one module of each type (engine, gun, suspension, radio, turret).
I'll look at the changes to tier 2 later, but for now, here's what's going on with the tier 1 tanks.
The thing which stands out most about the MS-1 is its high penetration compared to other tanks of its tier. In 9.14, it will lose the gun that gives it that recognition, falling back to 40mm standard penetration. The alpha is also worse, which is probably more of a big deal in today's meta. It otherwise has all the top modules it had before except for its engine, which is the 55hp module instead of 70hp one. Compensation comes in the form of better tank traverse, up to 48 deg/s from 38.
The gun lost here is strictly worse than another gun it keeps, so no real loss occurs. Like the MS-1, it doesn't keep its 100hp top engine, instead keeping the 85hp one. Also compensated with a massive tank traverse buff, up to 66 deg/s from 40.
Loses the top gun and falls back on one with less penetration and accuracy. Top engine is kept. Tank traverse buffed from 38 deg/s to 42.
Perhaps one of the biggest winners from the recent map changes as it was able to effectively use the high-penetration, medium-accuracy Raccourci without having to worry so much about the distance cap. Scratch that, the Raccourci is gone in 9.14. Also keeps the stock engine, losing 61hp to end with 39hp, which is laughable. Tank traverse buff is to 60 deg/s from 30.
Vickers Mk. I
Loses the autocannon, which was never a reason why anyone should have played this tank in the first place. Stock 90hp engine is kept over the 110hp top engine. Tank traverse buffed to 35 deg/s from 28.
No changes. It was released with this change in mind already.
Loses the autocannon. Top engine kept. Tank traverse buffed anyways to 60 deg/s from 38.
Loses the top gun and 10mm of penetration as a result. The autocannon now has more penetration than the available standard gun. Top engine is kept, but the top radio is lost instead, losing 50m signal range from 350. Tank traverse buffed to 40 deg/s from 36.
It appears across the board that engines for these tanks are getting nerfed and tank traverse is being buffed to compensate for rotational mobility (loss of upgradable engines = weaker tank rotation, more on that here), though it doesn't appear to be done with much consistency or as a balance mechanism. Most tanks will turn as well as they did before, but probably struggle more to get around the slopes of Mines. There are also firepower nerfs across most of the board, which puts all of the tanks in pretty bad shape to compete with tier 2s, especially the ones that had the best chance (T1 and MS-1).