Death Guard are known for their somewhat slow and unrelenting approach...their heavy weapon of choice? The autocannon, a very long range weapon. According to Blood Gorgons, almost all their tactical squads have one. My point? Autocannons have long range. Would it be really that bad having it with 45cm batteries, even with a price hike? It's not the end of the world, but death guard can have long range stuff too
All in all that profile is such an improvement its amazing. It's not worth slightly more though? Not that i'm complaining...
As for the scion, since we are going with a long range theme with it, in addition to the 60cm battery range lets drop a lance strength on the dorsal and boost that to 60cm as well. If we get rid of the torpedoes, the option has to allow you to buy Strength 9 torps (because fluff but also to make it equivalent), although I'm not sure a named vessel should have options.
Although to be perfectly frank, I think the Scion is fine with just the lance/battery range increase and the torpedo markup, even if it means a price hike. This thing is a freakin' beast with these changes: it might only have okay firepower, albeit at long range, but it can(would) be able to pump a Strength 9 torpedo volley alongside a Strength 9 AC wave. Maybe the changes above would put it at 475ish?