You may want to consider the following. The 'swing' tackle this year was Barron. No one thinks he's coming back. So who is your 'swing' tackle this year. The benefit of Smith is, while starting at RT he could serve as your 'swing' also. This will allow the Boys more flexibility on game day as your backup LT is already on the field and into the flow of the game.
Smith, if he is the pick, addresses two needs. A starting RT and back up LT in case Free goes down. As of today, we do not have a backup LT which is one of the most important positions on the field.
Given Smiths age, he could project to be the long term replacement to Free. I like Free at LT. If and I say if, Smith can handle speed rushers 1 on 1 and Free can handle his man 1 on 1, the passing game will explode.
For sure the OL and DB have to be addressed. I do think Smith is the consensus top pick at OL. I think Peterson is the top CB and I'm not a fan of Prince (I can't get that Blackmon abusing out of my head) and no FS is worthy of a 1st round pick. Of the areas of need and going with the BPA, Smith would seem to marry need to talent.
Last item, the entire draft is about projections. D. Ware never played OLB prior to Dallas drafting him. Ratliff never played NT prior to being drafted. The list goes on and on, but the draft is about projecting. There are no sure things in the draft but if you can lean on talent and work ethic, I think you will be right more than wrong. By all accounts, Smith is a very good run blocker and has excellent feet (LT worthy) and very long arms. Clearly he is dedicated, he benched 29 reps with 36 inch arms - no small task. So he has talent and work ethic, so in my book he is at least worthy of all the consideration he is getting.
JMHO