Very well done, an awesome compromise. Gives a strong reason to play daily without losing out on ability to rank well for weekly competition, and you're not potentially losing anything "exclusive". And the possibility for extra seals will allow some of the smaller guilds to hit 40k as well, encouraging even more guild participation. Brilliant!
I like that the rewards are ONLY available in guild wars, it will encourage people to keep playing when the same card comes around so that they can ascend it. I also like the general idea of being similar to the guild guardians, in that they will be generally useful or competitive cards that might actually make it to our decks and affect the meta. But as @Tacet mentioned, some of the current guardians are a little too powerful (2 of the 3 main teams I constantly face rely on a guardian). This is likely a more general balance issue than GW specific, but hopefully it's being considered and will be addressed.
HARD NO to this, I hope. If rewards are based on a points target, than it's not a "war", it's just like the weekly events were you just need to complete certain tasks. My understanding of GW was that it was to be a direct competition between guilds, meaning rank matters. I'd agree that the current PvP rewards pool is too small, and I'd hope the GW pool is bigger and maybe proportional (so ranks are "Top 1%", "Top 5%", etc. rather than "Top 5", "Top 25"). I'm looking forward to races where a few guilds are fighting over the last reward spot for a certain level, but if they all end up getting the reward, I fail to see the drama or competitiveness.
"Could", sure, anything is possible. But what your describing sounds far beyond the scope of anything that's been released or suggested so far, and this seems like a non-trivial change to implement, so I highly doubt it.