1. An indicator that shows when your hand is revealed to other players.
When your opponent plays a card that forces you to reveal your hand, it is easy to forgot to hide your hand again, since the only indication that your hand is revealed is the message in the feed that says "username reveals his hand".
Suggestion: a static highlight of your hand in red/blue/some other color when it is revealed - similar to the highlight that appears temporarily when you "touch" your hand.
2. A way to sort decklists (in the crtl-e popup window) by converted mana cost, card type, or other criteria.
Sorting by converted mana cost allows you to see the mana curve for the deck, which is very useful. Sorting by card type alows you to display the cards in a way that is more intuitive than color would be. (i.e. how most decklists on websites are displayed - sections split by card type.)
3. An addition to the output of /deckstats that displays converted mana costs.
For example, "cmc 1: 4 cards, cmc 2: 8 cards…" Or an output like "mana curve: 4-8-12-12-…" meaning 4 cmc1 cards, 8 cmc2 cards, 12 cmc3 cards, etc.
4. A "fieldnuke/reset" command to take all cards from your side of the field, your graveyard and your exile and shuffles the into your library.
A quick way to reset a game with a lot of permanents in play would be useful, e.g. when you are testing a deck at a 1 player table.
r518 fixes points 1 and 3. For point 1, my solution is to put the text "Revealed" on the hand, just below the card count, in orange text so that it stands out. Unfortunately this prevents the text from being visible when you have a 0-card hand, and I already foresee problems with the message desyncing from reality if players reload a game that was abandoned when one of the players had their hand revealed, but I don't foresee too many problems with this solution.
The border color of hand objects is buried at a very low level in code, and isn't structured for modification at all. Rewriting that class to expose the necessary variables would require a client recompilation at the least.
Point 4 has been fixed for a while in my custom Zonechange.command that supplants Fetch, but you already knew that.
Update on 1: I found out that the "fgcolor" attribute of a hand does in fact set the border color, without covering up any dead space in the corners of the hand object like bgcolor would. r600 now has it so the hand is outlined green in addition to the "Revealed" text, which is a change that shows up even with 0 cards in hand.