2013 Subaru XV Crosstrek -- 3 across help!

DS1 (3 yrs, 39" and 34 lbs) is in a FF Britax Boulevard G3 behind driver
DS2 (9 mos, 28" and 24 lbs) is in RF Britax Boulevard G3 behind passenger
Baby 3 coming in December 2014 (eek!)

The Crosstrek is brand new and we love the amazing gas mileage (avg 25/30 mpg in SoCal) so buying a new car is not on option list. DH has a company car (Jeep Grand Cherokee) from employer & no personal use allowed. DH not really on-board with changing out car seats unless I can get reasonably good deals on replacements and sell existing for close to covering cost of new ones -- he's an economist so the solution needs to "pencil out" for him to go for it. We do long-ish road trips (6-10 hrs to NoCal, Vegas area, Grand Canyon) and are headed to Italy in September with DS1&2 so seats will need to go with us on planes & into whatever rental car we get there.

I'm thinking about doing one of the following in Crosstrek and need help figuring this out:
(1) selling 1 Boulevard and getting 2 Cocorros for DS2 & Baby 3
(2) selling both Boulevards, getting 2 Cocorros DS2 & Baby 3 and something else for DS1 but no idea what

Should I do option 1 or 2 or something completely different?
Thoughts on how to configure backseat -- leaning towards the 2 RFs being by doors for easier loading/unloading with FF in center (more leg room & better view for him that way)? Suggestions for something other than Cocorros for the RFs?
Suggestions for what to get for FF toddler?

Please let me know what you were able to do with the Crosstrek! I also have a 2013, with a 5 1/2 year old in a booster, an 18 month in a rear-facing carseat, and a baby due in March, so I am panicking a bit about how to fit it all in! Any suggestions would be greatly appreciated!