I thought of a possible work around, it's a little risky but let me describe it to you.
1) Configure a Pi locally to you with your desired services including the rmt3 one.
2) Copy all of the /etc/weaved/services/*.conf files from this Pi to your remote device.
3) Copy all of the start/stop scripts, e.g. Weavedssh22.sh from /usr/bin.
4) Update the /usr/bin/weavedstart.sh to also start the Weavedrmt365535.sh upon reboot.
Now you reboot, and if all goes well, the remote device will now assume the identity of the unit you just configured locally.
If you want to reduce the risk, you can rename the conf files and .sh startup files so that you would not initially be replacing your old ones.
For example, on your new unit, you would wind up with a file /etc/weaved/services/Weavedssh22.conf, and a start/stop script /usr/bin/Weavedssh22.sh. You can change the name of the enablement file to Weavedssh22a.conf. Then edit the Weavedssh22.sh to refer to the new enablement file name.
Call this file Weavedssh22a.sh
Do the same for your http service.
Now edit the /usr/bin/weavedstart.sh to refer to these new file names. Reboot your local Pi and make sure this modified set of files all work properly and the device shows up in remot3.it.
Once you've done that, you can now copy the modified Weaved*.conf and Weaved*.sh (but not the weavedstart.sh) files over to your remote device. Take your local device offline.
Now on the remote device edit /usr/bin/weavedstart.sh to add entries for the three new services, leaving the existing ones in place.
Now you can execute sudo /usr/bin/weavedstart.sh on your remote device, and it should start your 3 new services, alongside the 2 already there. This device should now show up in remot3.it.
Once you've confirmed that this is all fine, you can connect with your new SSH connection and edit the /usr/bin/weavedstart.sh to remove the reference to the older startup scripts. Then, when you reboot, only the new services will be started.
You should make sure your "personality transplant" source device is never put online after that because our system really does not like two different devices phoning in with the same identifier (UID).
Let me know if this makes sense and you think you can do it. It's certainly a last resort but I think it should work.