My two cents worth:
1. An offline client, allowing you to play campaigns against bots /
- if it was combined with a strong bot and was sufficiently standard to be rated that would be good, but not essential.
2. A bot with a setting for different play styles
Even better would be a Bot that analysed a human players strategy and modified the bot-tactics as required.
3. A strong bot.
Stong bot is a good bot!
4. Options for timed games
Yes two different implementations spring to mind:
A. Each player gets a total time of x mins (ie. I just want a game that is between x -2x minutes long)
B. No player can spend more than say 2mins more than the other player throughout the entire game (ie. penalise go-slow players). This then allows for more complicated decks that do actually take more time per turn.
5. Options for undo settings
Sounds reasonable (always allow, allow if no cards drawn, never allow etc...)
6. Online mini-tournaments; the option to easily create one for you & your friends.
That would be a fun addition.
7. Option to invite specific players to your table
Not of use for me
8. More translations (to what language?)
Hasn't been a major issue for me as an English speaker...
9. Better animations when cards are gained/bought/played/...
10. Better visualization of split piles, Archive/Crypt contents, Prince targets, ...
Yes, Archive implementatoin as a priority!
10. Option to hide the log
only to show something else briefly...
11. Android app (or just improved compatibility?)
Apple user here
12. iPhone app (or just improved compatibility?)
Not sure how an iPhone App would work... iPad - sure
13. Downloadable game logs
not a big one for me.
14. Improved moderation (dealing with chat abuse, slowplayers, ...)
I've had a few issues with this but never bothered reporting as it seemed too hard... So yes!
15. Tutorial on how to play Dominion
16. Tutorial on how to play dominion online.
My username: RedMcC