I think Hosmer is certainly your stud 1B going forward, but it doesn't mean you can't have 2! Especially in your format. I think the trade is fairly even. Ellis to Phillips is about the same as Gonzalez to Pena. However, you know your league best. What could that extra FAAB get you? A difference-making closer? or not much at all? I like that Phillips is around another 2 years as compared to AGON for only this year.
Also, take into account what you could buy next year with the $33 of AGON coming off the books. How is the inflation in a league like this? Are you getting stars for $35 or are they going for $50+? Who else is a FA?
Assuming the FAAB isn't a massive factor for you, and that there isn't a difference maker you can sign with the money at the end of the season, I think you can do the deal and improve your 2013 and 2014 roster. In a traditional league setup I would not make this swap, but I think your mitigating factors makes this a "yes" for you.
Take a look at mine if you'd likeviewtopic.php?f=26&t=444362