I have a rules question for you fine people. It centers on what happens when a PC gets a new suit of armor (like artificer armor or terminator armor).

For sake or argument, lets say that at character creation the PC started with MK 6 "Corvus" Armor and created power armor histories from RoB. Later in his career, the Marine upgrades to Artificer armor using signature wargear. Does the PC effectively upgrade his armor on all locations? Or does the PC have to generate 2 new power armor histories and "give up" the Corvus armor - losing the +10 to agility and the suit's associated histories - if he wants to wear the artificer armor?

Thanks for your help.

outside of the techmarine (which you could argue is an upgrade), buying artificer armor is a new armor. You have to reroll histories. Same as if you go terminator.

To get an artificer armour, you need Signature Wargear (Hero). The talent's description doesn't say whether it needs to be a completely new one or an upgrade, although Signature Wargear (Master) specifically allows upgrades.

I'd say it's up to your interpretation as a GM - in my case a Techmarine's armour would definitely stay the same as he painstakingly reworks and upgrades his own suit, but not so much in a different Marine's case, where they usually get a relic off the shelf or altar, and not a re-work - just as Kamikazzijoe says. Note, however, that Rites of Battle explicitly allows the player to choose both the mark and the history of the Power Armour with the GM's blessing (RoB, pp. 152-153), so in your example your player might opt to take a different Mark VI suit with new histories, or even the same suit with one additional history rolled.

This should have a good in-universe reason, like the player did a favour to the Armamentarium, and the Master of the Forge owes him one so he upgrades the suit, or some Captain pulls some strings to get the same Mark for him from the armoury, but ultimately whether you choose to introduce the new item as a replacement or as an upgrade has nothing to do with RAW.

Terminator armour is a whole different beast - you can't get it as a Signature Wargear, as it costs 100 Req, so it's definitely rolling (or, again, choosing) something new.

To get an artificer armour, you need Signature Wargear (Hero). The talent's description doesn't say whether it needs to be a completely new one or an upgrade, although Signature Wargear (Master) specifically allows upgrades.

I'd say it's up to your interpretation as a GM - in my case a Techmarine's armour would definitely stay the same as he painstakingly reworks and upgrades his own suit, but not so much in a different Marine's case, where they usually get a relic off the shelf or altar, and not a re-work - just as Kamikazzijoe says. Note, however, that Rites of Battle explicitly allows the player to choose both the mark and the history of the Power Armour with the GM's blessing (RoB, pp. 152-153), so in your example your player might opt to take a different Mark VI suit with new histories, or even the same suit with one additional history rolled.

This should have a good in-universe reason, like the player did a favour to the Armamentarium, and the Master of the Forge owes him one so he upgrades the suit, or some Captain pulls some strings to get the same Mark for him from the armoury, but ultimately whether you choose to introduce the new item as a replacement or as an upgrade has nothing to do with RAW.

Terminator armour is a whole different beast - you can't get it as a Signature Wargear, as it costs 100 Req, so it's definitely rolling (or, again, choosing) something new.

Terminator Armour is not 100 Req as is explained on pg 164 "...when Requisitioning Terminator armour, the Battle Brother pays the 60 Requisition Points for the armour itself and then must spend a minimum of 40 Requisition Points to arm it."

On pg 126 Sig Wargear Hero states "Select from the Armoury (excluding unusual ammunition) with a Requisition cost of 70 or less." Thus putting Terminator armour on the list of items that can be selected with Sig Wargear Hero, all you have to do is put 40 Req worth of stuff on it, otherwise you can't use it.

You're partially right, core rules can in fact be interpreted as such, but Errata FAQ on p.9. clarifies the question:

Question : Can a Battle-Brother take Terminator Armour with Signature Wargear (Hero)?
Answer : No. Terminator Armour’s total cost includes the integrated systems, totalling over one hundred Requisition, making it out of the range of Signature Wargear (Hero)’s seventy Requisition limit.