For the Churchill:
I reckon shift 60 armour from the back to the front (300/120), reduce hit points to 800, 0.8 received damage.
That gives it 1000 effective hit points and +25% repair speed. That's a seven shot kill from an AT gun, same as the IS-2, Tiger, Croc and AVRE. (The live Churchill is a nine shot kill).
Move the smoke shell from the Crocodile to the standard Churchill. The Croc has a flamer: it doesn't need to blind anti-tank guns. The standard Churchill, however, would definitely appreciate it.
For the KV-1:
Give it the same armour values as the KV-2: 300 frontal, 120 rear. That makes the KV-1 a little better at range, but rewards flanking it.
The churchill and KV-1 won't be worth using at range suddenly just by giving them more RNG dependant health pools, nor will making the Church a random gamble on it dying before it even gets close enough to throw a grenade.
The Tiger/Pershing as heavy tanks work with the high front armour but more punishable flanks/hp pool because they have two important characteristics.
1) A good gun that is punishing at all ranges
2) Decent speed so they can engage and disengage when they need to
Neither the KV or the Church have either of these. Without them they have no job or purpose trying to be used at long range. Their entire design philosophy is contrary to a style of play where they are used at long range. The Churchill has most of its AI in a dang grenade throw.
By contrast, the KV2 (and ISU, its nearest counterpart) and Brummbar all have high front armour, mediocre mobility, but an enormous
amount of firepower. Also not something you can say about the Churchill or KV-1, so they can't fill that role either.
Making their HP pools more RNG dependant with more armour and less effective HP, you're making their actual job a coin toss on just being an immediate death without the mobility to ever be able to retreat, because they're also too slow to retreat if the bounces don't work in your favour when you push.
So unless you want to up their front armour, lower their rear, add a 17pdr to them both with a decent AI profile... and then up their cost and call them KindaATiger? No. Sensible sounding changes that would only make both units garbage.
Flanking a tiger using its range properly is bloody hard
Flanking a churchill using its grenades properly requires moving forwards five feet