I am sure you know most free games are only seen for a few minutes a day by the masses, where they'll usually collect or spend their daily stuff. Make sure there is randomization or it will not be entertaining to revisit each day.

Facebook games and some Mobile games perhaps, but AAA F2P, certainly not, and many other PC-based F2P are rather immersive.

How many game transitioned to 'Free to Play' after running as a pay to play game for a substantial time already ???

They had a chance to make money the old way first and then to milk something they largely already had paid for using F2P mechanisms.

How much different is trying to do the F2P from the start ??? These days unless it is a pretty good game players will play for a while and then grow tired of it. If they can do that 'playing' in F2P mode and then bugout, the company not only didnt get the money for the dev, they had to pay to have the player play for free.

Can the popular theme carry them through to continue playing to want to purchase additional components??

Some games require the 'bought' items to play (to even survive) in the advanced parts of the game (Raids or whatever).

Can you build a NEW game with enough draw to get the players involved enough to actually pay for it (since you will be offering a way to play without paying...)

I'm going to point out to Bethesda's The Elder Scroll Online and Final Fantasy XIV.

Possibly, the subscription model might make a serious comeback here, and F2P isn't so much the future as it may be "an option".