Hello Bikash, 5x3 pooja room is not a big one. However, it will be a good idea to do the civil changes you mentioned.You will get additional space that ways . What do you plan to do with that new space. We see a beam in that area, keep that in mind before you proceed with the changes. Wall mounted pooja unit is doable in multiple areas as per the plan. Do you have the directions mentioned in the floor plan to suggest it as per Vaastu. Thanks Nitin Cornerstone Designs Bangalore.

For a new home , get a new Pooja mandir , get is customized according to your place . https://www.houzz.in/projects/2968210/pooja-mandir-with-gold-plated-accessories-in-chennai

Are you referring to any specific plan ?

If your living room on a separate area so you can place a furniture in 2 ways ( 1st is Modern sofa & Table ) 2nd is Traditional Look Sofa & table & If your living room is near by kitchen or a Hall type area you can place sofa set with table & Dining table for 6 people's