The Leman Russ flexibilty, to have 10 battletanks for 625 is a very comfort change. I would love it!
For Artillery Company, I think there is quite a big agreement in cost reduction.
For griffon part, some time ago I used to take them, but was never really satisfied with it. I think they just can't fit in neither formation, not even mech. inf. coy. First of all; most IG companies are perfectly viable on their own, they don't need firepower booster, and it is also more benefical to spend the points on activations instead of upgrades (except hydras).
What I would like to see and is a big change, to add them as artillery battery option. 3 units for 200.
They are cheap 3BP that may put out the same firepower as a basilisk, should the opponent approach too close.
After or before that, they are 30 cm moving AV, 5+ FF, these adds up to very useful later turn options, not to mention it's uniquity and character it could bring to the battery palette!
50 points upgrade for 3 griffon is something that is extremely cheap, and just wierd. (In this exact case I think it's not advisable to follow the UK route.)
I totally agree with Paradox, regarding Hellhounds - cost and armor reduce. (I found hellhounds really cool for 125 as well, it will be superb to have some on 100!)
Baneblade is already on the table, and is already a good choice. All it needs it's main gun receieving some AT love. Currently my suggestion for that, to change the main gun from 1x AP3+/AT3+ to 2x AP4+/AT3+. It has been tested in battles with 2x AP3+/AT3+, where the AT power on it's farthest reaching weapon raised it's level to acceptable, while the AP power slipped over the top, so that's the reason to make them different.
Basilisk, Bombard, Manticore... the batteries. Honestly idk this part. Used every variant many times. And each variant was very cool for me. I think the balance here is so fine, that it only slides away if we add combos and opponent armies into the box. 2x manticore battery is an excellent formation breaker, but if you have only 1x, it may not have the opportunity to place that much BM to do the difference.
Whenever I take 1x battery, I mainly do with basilisk for resilience and ad hoc direct fire opportunity, it's very cool.
Recently I have started to go with bombards, and I think they aren't that bad; many times the ignore cover ability and 6 BP generated so much punishment that no other variant could do, not even Manticore!
It's just perfect siege artillery, excellent garrison breaker!
If you have at least one bombard formation and couple of shadowswords then you have completely covered the two edge of formation stereotypes the opponent would field; the smallest (quantity) and the largest (quality).
Considering all these options I really don't know wheter the arty battery needed to be changed at all. (Apart from adding griffon option for 200
)
My two cents.