Kishore,
It is all valid scenarios, and assumptions. I have had the privilege to work my self and with team members on various scenarios.
BW on HANA
HANA Side Car
HANA Enterprise
HANA Cloud
more than just the technology solution, I think you need to provide details as to:
1) how ready is your current system to make the switch?
2) is your organization ready to go a full blown solution or wanting to do a side car approach to make sure you and your organization is ready?
3) do you already have access to hardware or a cloud certified partner? (Hitachi Consulting
offers both services, however, HCP and AWS are other options on cloud)
4) how big will your data footprint be? this will determine the hardware sizing.. make sure you do this as I have been involved with customers who did it incorrectly and have struggled with performance.
5) do you have a team with knowledge in HANA / BOBJ / BW , etc? We do, make sure you do not underestimate the resource training. There are many certified partners that can help you with this.
there is more but these are some of the first few questions you should ask and get answers before you jump into what type of HANA approach you should go for. Hope this helps.. feel free to reach out directly for more information