I don't know if I'm one of the people this qualifies for, but I'll respond anyway.
1. An offline client, allowing you to play campaigns against bots
Not of interest to me, having played many tabletop games in app/online form, although I appreciate it's an option, I get bored of playing against something that's running a script. At top levels of play, it's easy to predict and "game" the AI. (I'm not top at Dominion, but was a competitive Catan player, and get super bored of playing the bots).
2. A bot with a setting for different play styles
If you do it, yes, this is better than just one script that all bots run. Carcassonne does a great job with this, for example.
3. A strong bot.
As strong as you can make it, yes!
4. Options for timed games
Yep might as well, lots of people like fast play. It's probably one of the most common complains in in-game chat. "play faster please".
5. Options for undo settings
I like the current setup of undo needing to be validated by other players. Maybe a way to toggle so it is/is not an option for any more that reveals information.
6. Online mini-tournaments; the option to easily create one for you & your friends.
Yes! This would be awesome! Friends, and also rando's. I'd love if I could play a mini tournament any time.
7. Option to invite specific players to your table
I don't care but I'm sure lots of people would want this and it would make sense.
8. More translations (to what language?)
n/a for me, only need English.
9. Better animations when cards are gained/bought/played/...
Hmmmm...maybe, but not at the expense of slowing down play. Maybe if you can toggle them on off.
10. Better visualization of split piles, Archive/Crypt contents, Prince targets, ...
Yes please, anything you can do here. And maybe I just don't know where it is, but ability to view the various mats.
10. Option to hide the log
Sure, maybe just minimize it to the side.
11. Android app (or just improved compatibility?)
n/a for me, but yeah seems like it'd make sense.
12. iPhone app (or just improved compatibility?)
Yes. I would play it all the time. Was playing the MF one a lot.
13. Downloadable game logs
Not of interest for me.
14. Improved moderation (dealing with chat abuse, slowplayers, ...)
Yes, maybe more ways to deal with slow players, maybe a setting people can agree to before starting the game of how long before a "time out" can be dealt with.
I don't mind swearing in the chats, and actually like it, but derogatory language should absolutely not be allowed!
15. Tutorial on how to play Dominion
Not of need or interest to me.
16. Tutorial on how to play dominion online.
Yeah, with any product, you want people to be able to use that version of it, so where buttons are and how to change settings should be explained some how some way.