The rules for "all words valid" scrabble are exactly the same as ordinary scrabble, except that every single combination of letters is in the dictionary. To make the game deterministic, we will also assume that every letter is worth the same amount of points (though it may be interesting to remove this restriction somehow)--so essentially it is just a game of placing tiles. Is there a winning strategy for either player?
'Pass' is a valid move in Scrabble. This means that a game can last for ever, so you need some criterion for ending the game after each player has passed. It also means that the game is either a win for the first player, or a draw (because if the starting position is losing, the first player can pass).
If you don't allow passes, then I can't see a way of calculating who wins. It looks more complicated than Draughts, which succumbed to rigorous evaluation only after years of dedicated effort -- see http://www.sciencemag.org/cgi/content/abstract/1144079v1.
I have some experience in these matters -- a Scrabble program I co-wrote won a Computer Olympiad gold medal many years ago.
I'll try to kick things off...
Are there still double/triple letter/word score squares? I imagine the strategy would focus on putting down all your letters while aiming for these bonus squares while trying not to open up the board (to restrict your opponent's access to them)?