Very, very nice team considering the depth of your league.
There are 750 total players in the MLB, and your league has 500 of them on rosters, so sick (as in awesomely competitive).
Your OF is very solid, and I agree that 1B could improve. I'm more risk-taking, so I'd probably trade Ichiro for some younger SP and/or 1B, UTIL help.
The thing about OF is that there are ostensibly 90 MLB starting OFs (as opposed to only 30 MLB starting 1Bs), which allows a little more room for you to get lucky with shrewd WW moves. There are 30 OFs who are starting in MLB but are NOT starting in your league; there are presumably 10 1B who are starting in the MLB but are not starting on a team in your league. That's my long way of saying that I'd prefer to pick up a solid 1B and perhaps look for WW OF than the other way around.
Even though your league is deep, you ought to have a better 1B. First basemen ranked in the 18-23 range are usually guys like LaRoche, Derrek Lee, C. Lee, maybe Sanchez, Smoak; your 1B are presently well below those guys.
Theoretically, if you had the 20th best (i.e., the worst) 1B in your league, you should have someone like LaRoche... so a guy like Trumbo is theoretically worse than the average last-ranked 1B in your league. Of course, by focusing on other positions you also are well-ahead of league averages, like at OF. You don't want to fall too far behind 1B production as they are obviously the most productive hitters (the difference in stats between the 20th and 1st rated catchers is smaller than between the 20th and 1st rated 1B).
With Ichiro, I'd target Kila Ka'aihue, Gaby Sanchez, Brandon Belt, et al. I think something like Ichiro for Kila/Tabata/Gregerson would be reasonable, though I have no clue what trade values are like for a league like yours.