How to make a pay-to-rawmultisig transaction? Using the default client's RPC calls, can I make a transaction that sends to a RAW multisig (not P2SH multisig) scriptPubKey? 

If I made a raw transaction, and edited the bytes in the scriptPubKey of one of the outputs, could I manually write in my own scriptPubKey? Hopefully, instead of doing this manually there is either support in the core client or there is a tool out there that I don't know of that can help.
No, Bitcoin Core doesn't have any RPC calls which allow you to create a bare multisig pubkey script.

Yes, you can create your own pubkey script and insert it into a transaction.  This isn't hard---but it is dangerous.  One mistype and your bitcoins are lost forever.  Note also that greater than 3-of-3 bare multisig pubkey scripts are non-standard, so they won't be relayed or mined by standard clients.

What might be challenging is spending the output at a later time---you will need a program that understands how to correctly sign Bitcoin transactions using an arbitrary private key.  Bitcoin Core can do that if it either has stored or is given all of the private keys necessary, but not all wallets can.