I am so glad that MTGO has a solitaire option because it enables me to use my gigantic casual stash of cards. I wish there was a format other than solitaire that allowed me to do so. Playing against real players will have to wait for these decks, though. Here are some restrictions that would enable that type of real play:
1. Your deck can only have at most two of a non-land card. (This is what I would refer to as the Hearthstone rule.)
2. Your deck must have at least 14 creatures.
3. Your deck must have four planeswalkers, one of each.
4. Your deck must have cards from exactly three blocks from Mirage to date. It can be any three blocks. Lorwyn and Shadowmoor are considered separate blocks. You can substitute any one block with the core sets and Tenth Edition as one block-this would be a gigantic selection of cards, but many were reprinted across many of these core sets. Reprint sets (Vintage Masters, Modern Masters, Eternal Masters) are considered as core sets but one of these sets corresponds to a block. For example: you can do two blocks from Modern and Modern Masters. Coldsnap is the odd set but its not out, it does go in Ice Age block... we will have to wait until MTGO has better coverage of the very early sets to add Coldsnap to this format. Once MTGO covers all sets, we can group the early sets in fake blocks for inclusion.
5. Black border only. White cards look terrible.
6. Legacy ban list.
With these six restrictions there would be a mix of casual cards and powerful cards that would enable all those poor limited jank cards of old to be played again. Here is one such deck. The three blocks are, of course, the blocks in my Superguild cube.
The deck has a reasonable mana curve.
Here are a few solitaire games. In game 1 I dropped a few creatures and finished on turn 7.
Second game I got to play two planeswalkers. The deck hits in low numbers but has solid evasion and the ability to stall with tappers.
Game 3 I got mana screwed, yet still finished on turn 7.
Game 4 was really fun (well, as much fun as solitaire can be, and Storm players know a lot about this.) I would have close to a Tamiyo ultimate in this one.
I finished turn 8.
Game 5 I got to play Jace, the Mind Sculptor (JTMS). JTMS slows the game some, but the draws become really stable and I set up for a solid game. As someone said once, JTMS can take a game over for you. I finished turn 10.
Game 6 I also got to play bigger creatures and finished really early for such a slow deck on turn 5.
Game 7 was another JTMS slow blow-out, this one on turn 7.