Is there a way to force a message to be sent as an MMS?
Force the MMS
I've saw this comment you provided on your question:
If this is the case, you can have a
As far as I know, you can't.
An MMS message is a plain old text message with contents attached.
If you attach a media file, it will be send as a MMS message. Otherwise it will follow as an SMS.
As per Broam's suggestion above, I'm posting my comment as an answer. Hopefully some people finds it useful.
If you add a Subject to the message you're making, it gets converted to MMS format. Even if the Subject is empty, at least, that's what I know
I've found that another option, on phones or text messaging apps that support group texting but that don't force MMS when you add a Subject, is to create an artificial 'group' consisting of the person you're texting to .... AND yourself. In other words, send the text to the target person AND yourself. If you've got group texting support, doing so will force an MMS, and thereby bypass Google Voice. Hence, your emoji will get transmitted in spite of Voice. Once you send the group text, you will receive a redundant copy of your text. At that point, just delete it. This approach can become a little messy if you don't know what you're doing, but it works for me.:-)