Supersub? Give me a subsub any day

"Supersub strikes again!"

- Gerald Sinstadt, ITV commentator, after David Fairclough scored the winning goal for Liverpool against St Etienne, 16 March 1977 (sources: Wikipedia and Bobpaisley.com)

I have absolutely no problem with the 12th man playing an active role in a game of cricket, and I believe that there should be situation in which he/she can bat or bowl in a game, so long as there are always eleven versus eleven at any given moment.

I do think, however, that the rules currently on trial in ODI cricket (Standard One Day International Match Playing Conditions 2.2) need a bit of refining, but not scrapping. This is what I'd like to see:

1. Captains permitted to name a squad of twelve players before the toss.
2. The twelfth man nominated after the toss is made.
3. Substitution be allowed only at the half-way point of the game (ie, at the conclusion of the innings of the team batting first).

I think that's pretty fair and simple. Thoughts?