Moto G XT1033 as it seems from this question supports OTG, which means you can connect a pendrive using an OTG cable and store complete Nandroid backup in it through the recovery.
Will I be able to return to system with Phone (sim) and Play Store apps working through the "system" backup?
I cannot comment anything about Baseband/IMEI issue, but you will definitely lose Play Store apps since they are downloaded and their data stored under
/data, which you're not backing up here.
On a side note, the device has good amount of Internal Storage available; can you not make space enough to store the backup in it?
May be you can try making a backup of
/system only and then pushing it through ADB into the PC. Do the same for
/boot now. ADB will work in Recovery.