It is absolutely possible for a baby to start the night in a separate bed and join you later in the night. Absolutely. My children both did it. It worked great and gave us all a good combination of uninterrupted sleep and cuddle time.
A lot of people think that Family Bed is all or nothing, and they will give you guilt, because you're not fully doing the "AP Checklist" that they think has been ordained as the one AP Way. They'll say things like "kicking her out of the warmth" or "confusing her with your inconsistency," or even, if they're feeling particularly smug, "this is such a relatively short phase of her life, suck it up." They aren't helping, and they don't represent anything but their own black and white thinking.
THere's lots of evidence that depressed and stressed otu mothers are more permanently harmful to children's development than having to sleep separate for part (or heck, even all) of the night. AP is about responding to your child's needs -- all of those needs, of which sleep is only one, and a healthy mother is another one.
Human children evolved in a world where they slept in lots of different locations: On mom's back, while she walked to gather; in grandma's arms while mom's arms needed a rest; on dad's lap by the fire; curled with mom in a pile of grass; cuddled with an auntie or older sibling; in a hammock made from a baby sling, strung from the rafter of a hut. They might do several or all of those in a day. This idea that there has to be One Place to Sleep and One Person to Sleep with is very absolutist.
How you get there depends on you and your baby. For us, from birth they were in a basinnette pushed up against the bed at the start of the night. They could hear and see and smell us and I could sleep with my hand on their backs. Later they started the night in the crib (which wasn't in our bedroom -- not enough room). We were in a tiny apartment though, so it was fewer steps to the next room than it would be in some larger houses in the same room! Given the time they generally went down to sleep, I'd usually still be somewhat conscious if they woke by midnight, and at that waking I'd nurse them fast, back down to sleep and back to their own bed. The next waking might not be until 4 or 5am, and at that point I'd bring them back to bed.
People will say "Oh, you get more sleep if they're just in bed and you can roll over and latch on and go back to sleep." For me, this wasn't the case, because I could not drop fully asleep while they were latched on, so even when they were in bed with me I had to unlatch them and close up my nightshirt top to prevent random access. The few times I thought "Oh, I'll get that uninterrupted sleep while nursing that everyone talks about," I slept badly (if at all) and woke up sore and resentful.
My kids weren't confused by part-time cosleeping. They prospered. I never CIOed, they slept well. My DD actually made it clear as a toddler that she liked more space than she got when cosleeping, and preferred to sleep most of the night sprawled widely across her entire bed. Tucked in and spooned with me and DH (and sometimes her older brother) she tossed and turned and didnt' sleep well.