Hyperstimm Backlash/Architects of Pain and Deepstrike

So I'm thinking of experimenting with large deepstriking wych blobs, and I am wondering if you can use the hyperstimm backlash and/or architects of pain stratagems in the same turn the units deep strike. Now I know both of these stratagems happen "at the beginning of the battle round", and that deep strikers are not placed until "the end of the movement phase". However, both stratagems state that you "choose a unit from your army". Nothing says pick a unit on the battlefield, or has any wording specifically stating you cannot use this stratagem on a unit waiting to deloy. The wording in particular makes me think it is allowed, choose a unit in your army is pretty general. Maybe I'm missing something though.

It's not terribly likely I'd be using one of these strats often on a unit that could very well not make it to cc, but I am curious whether it's allowed at all or not.

I'm pretty sure that to pick something, it does have to be on the battlefield. Like how you can't target units in transports with psychic powers.

Psychic powers aren't the same as stratagems though, you're picking a unit in range of the power that's on the table. These two stratagems in particular have a very broad target range, no real preconditions at least in the wording of the stratagems. The only thing that would really prevent that is if there's been a ruling on not being allowed to use a stratagem to target a unit if it's not on the table.

You'll probably find said FAQ along side the one that prevented WL traits from working on units not on the table.

Yup there is a FAQ on this specific sort of situation, can't target a unit in a transport or waiting to deep strike on the board. The transport part is an extra pain since wyches coming out of a raider can't use architects of pain.