You can set the size, but the minimum is ~1 GB IIRC. The main implication I see is that if you need to rescan the blockchain for some reason you have to redownload it, verify it, drop it. If you have a full copy you can do this locally. A pruned node is not less secure because it verified all data locally, it just does not keep the data. Its also not as helpfull to the network as an unpruned node as you do not relay old blocks and thus cant help others sync up.
Correct. Basically the most likely effect that this is going to have in an total increase in the number of nodes. However, it might be a bit problematic if a lot of full nodes switch to pruned ones. I do also wonder if there would be anything bad (in comparison to the current state of the network) if almost everyone was running pruned nodes?
Ok that would be awesome if it did.
It is highly likely. The only unknown factor ATM is the exact date of release, but the feature should come.
Well if a high number of nodes would be pruned it would be very difficult to sync a new node (pruned or not). If you consider that you only establish 8 connections and while syncing the nodes dont seem to create more connections, you will need at least 1 not pruned node out of 8 to sync.