StellarGuard Interesting discussion, I hope this thread gets attention and we can see many different opinions on this.
About point 1: In this idea, would the validators accept, but not act upon, any transaction as long as it was marked as "partially-signed", since it will eventually be resubmitted? Or would they validate the changes (like checking if the source has enough balance etc), even though they can't actually process the operations?
2 is actually like 1, because in both cases the transaction will be propagated through the network, validated, won't generate any effects, horizon will ingest it and save it in its database for the clients to later query and resubmit the fully signed transaction. The only difference is that in 1 the network user building the transaction sets that it is "partially-signed", while on 2 who does that is a validator.