Hi @supratim320
Yes, you can have a custom implementation of MMS. You need to create external connector and how this is done depends on the provider. In any case, you need a experienced person to write it.
As feature is deprecated, there is no packages to install and get everything done. You need to create forms for it, extend some schemas, etc...
You do not need separate channel as SMS channel has 3 subtypes (SMS,MMS,WAP) therefore you can re-use subtype MMS within SMS channel.
Regards,
Milan