Let's make Sony take half their Lemons back! The other half... make lemonade.
Valve will let you do it. They always let people do this kind of stuff. It is selling the mod without Valve's permission that will be the problem, assuming you do try to sell it (not recommended).
It IS possible to do that (porting Half-Life 2 Models into Half-Life 1). Back in Counter-Strike: Condition Zero, people have been doing it all of the time, and on a Zombie-Mod Server, all of the Zombies used the Half-Life 2 Zombie Model.
Sorry, meant to reply to another comment. I was trying to ask supe7nova
Also, the official page just takes me to some stupid Japanese Environmentalist Site
Are you one of the Developers?
If so, then you could start working with the Half-Life 2 Capture the Flag team, and you could create a super-mod.
Are you sure he's dead?