Here's a few things I'd like to see.
1. A special type of platoon (possibly under a different name - division perhaps?) that allows infinite members. This would allow gaming communities to have a presence on Battlelog without needing multiple platoons.
2. The ability to join as many platoons as we want. The 5 platoon limit in BF3 was a PITA to manage (especially when trying to accept new members into a platoon as it doesn't tell you that the member in question has run into the 5 platoon limit).
3. The ability to start missions that involve the whole platoon.
4. The ability for platoon owners to create an easily shareable link via a custom identifier (similar to how Facebook and Steam Community allow users to create a unique URL identifier to make it easier to share their profile links). An example of this would be http://battlelog.battlefield.com/bf4/platoon/DICE (the platoon owner would be able to change "DICE" to whatever they want within reason).