With DS - I had the arm's reach co-sleeper. I didn't figure out nursing side lying until he was 3-4 months old, so we'd sit up or go to a chair to nurse. Once that was figured out, he started in there each night, and then came to bed with us at first wake up and stayed there. When I had concerns at first about DH (when DS would nurse on the side between us) I kept a hand on DH to make sure he knew where we were in the bed. In time, DH just clung to his edge of the king sized bed, LOL, and left us most of it. Around 7 months or so, I put up the co-sleeper. I tried it on the bottom, pack n play sort of setting, but the mattress seemed uncomfy for DS. So then he started the night in his crib, in another room, and I brought him to bed when we were ready to sleep. between ages 10-12 months, I left him in the crib until his first wake up, and then brought him in with us. Shortly after that, he STTN for a few months, then stopped when I got pregnant when he turned 14 months and started nursing all night. I couldn't handle that (pregnant working mama needs sleep) and we night weaned and he went back to sleeping in his crib all night.
By the time #2 came along when he was nearly 2, he was sleeping all night, in a toddler bed, in another room, and hasn't wanted to come back to our bed.
#2 (DD) is a cuddly baby and didn't want to be separated from her food source, ever. Even in the hospital she slept in the crook of my arm and refused the bassinet. She slept on occasion in the bassinet part of a pack n play, but mostly just in bed with us. We nursed side lying from day 1. She stayed in bed with us all the time until right around a year when we transitioned her to her own big girl bed, on the floor, of her own room. She's done fantastic, sometimes wakes once, but being that it's a queen size, there is plenty of space for DH or I to lay with her in her own bed. Once we had moved into a bigger house, I bought a used IKEA crib to sidecar to our bed for extra space. I LOVE it. The new baby will be using that, I think, hopefully for at least part of the night.
Logistics: DH and I have separate, lightweight blankets that generally stay around hip level, and never go over the baby. We have limited pillows and only sleep with a fitted sheet. Honestly, this is all personal preference and how we have always slept, but comes in handy in regards to safety and co sleeping. Once baby is mobile, we have used a side rail for safety, and we teach how to get down off of the bed safely too. Now, honestly, all babies will likely fall off the bed once or twice. we have carpet, and I think it startled the baby more than anything. If we had hardwoords or some other surface, I would at least put cushy rugs down around the edges, if not pillows (or maybe some foam play mats - One Step Ahead sells some that actually look like hardwood floors)
On all of this, YMMV - I have had one child that always slept better in his own space, and never was super fun to co-sleep with (he twists and turns and finds a way to take up the whole bed - he wants his space that badly - and one that loves to cuddle, and sleeps best with her head in my armpit, literally. Who knows what this 3rd baby will be like?
I think we will probably still end up getting something that attaches to the side of the bed, but it's so helpful to remember that it really depends on the baby's personality and how things do or don't work as planned. I visited a friend this week who had a co-sleeper attached to the side of the bed, and it was a hand made one that snugged up really tight to the main bed and had a mattress at exactly the same level. So she could sleep with the baby on the "outside" of the bed, and if the baby rolled over it just rolled into the co-sleeper. Sort of like spughy's technique of having two mattresses on the floor!
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