Well 9 out of 10 things brought up in this thread are either already covered by the rules very clearly (like everybody knows Open Ground is Terrain and yet people ask for FAQ I don't get it), and then there's loads of these quite unprecedented 'balance-suggestions' which just seem off topic to be honest..
but of course one or two 'actual' candidates that would be good in the Errata/FAQ pop up too.
Being a Daemon Player I'm just gonna comment on the following:
With regards to Gifts becoming 'Magic Weapons' (0-1 Choices) I assume the implicit consequence of your suggestion here is that Daemons also get access to BrB Items.
If 'No' = *facepalm* (well you came to the right place..)
If 'Yes' = There are tons of Magic Items that would be quite problematic if Daemons had access to them. I'm not sure you've thought this one through to be honest.
With regards to Spirit Swallower it absolutely does not 'interact' with ThunderStomp. This is already covered by the present Errata/FAQ.
Daemonic Gifts are Special Rules.
Special Rules never interact with Stomp.
So that one you can cross off your list.