SEP 12.1 RTM Revamp

Hello folks, facing a scenerio need your suggestions and inputs to complete it in a suitable envoirement . Need to do a Revamp of an old SEP envoirement. Below is the current scenerio

• Single SEPM 12.1 RTM with a SQL database support around 1000 agents running same version as SEPM
• OS of SEPM is server 2003 and DB is SQL 2000 ( Its an old envoirement with physical servers) with low resources
• Currently 800 agents are offline ( not reporting ) and 200 online and connected
• No need to migrate the existing envoirement to a new virtualized envoirement ( having diffrent SEPM servers IP and hostnames ) with upgraded OS and more resources  

Now The question is which method is more prefereable and needs manual intervention at agent level ?

1. Should I do DR on the new servers of old SEP again install the same SEPM version envoirement and restore backup then upgrade to SEPM 12.1.5  ?
2. Should I install SEPM 12.1.5 from scratch on new servers then deploy communication update package on those already offline machines and try to move them to the new SEPM ?
3. How can I restore my offline agents which are already offline and move them to the new SEPM ( without manually reinstall and install the agent again ) . If the smc service is stopped, corrupted or not running in that case what would be the outcome or result of deploying communication update package ?

Which method is more seamless and optimum to do ? and which method invloves no manual intervention at the agent level ?

Regards