I would suggest that you should consider the rebuilding costs should you change your mind for any reason. 

Like the rewards for troop training are changed, or the extra rewards you may get from more training are outweighed by any costs incurred in the conversion. 

You obviously want to churn out troops as fast as possible,do you know what increased efficiency you will gain.

Can you first  do more research to increase training output?

Bad idea, with new items now for troop training capacity which even can drop in some competitions I don't rly see any plus in tearing down manors. 

You should do the opposite, leave at least 2 or 3 barracks and do manors rest. Especially if you are only a t1 user cos they go very fast and cost of boosts adds up over time you don't even notice it. 

I do not recommend you do that ... I only have one barrack ... so most 2 or 3 I recommend.  The manors reduce the amount of time to train so it's good idea to have a number of manors.

I also would prefer manors instead of Barracks. I have one Barrack rest Infirmaries and Manors. If you click on the Manor you see the % Training boost you gain. 

If you really want to train a lot of troops than increase knowledge for training. Use Inga the Wise, she has abilities to increase the number of warriors in training. Use Hero Training Gear and Hero Skil. Activate Training Boost Item and go for it. Those Steps really helping in decreasing Training Time. And if you have some Manors..I have 7 you are very effective with your Time Boosts.