We do not have issues today. You're being reactionary. I honestly don't think there is a single position we could draft at 15th in the first round where that player would come in and be an immediate starter over a healthy current player on our roster. Everyone we're drafting this year is for future depth.
Boone will not resign with us. He wants to make the move to tackle where the pay is significantly increased. There is no chance the 49ers sign him at RG for tackle money.
Taking late round OL picks is how you end up with guys like Looney, who just don't seem to cut it. Could a late round player make the team and play well? Sure he could (Kilgore), but Iupati, Staley and Davis are all 1st round picks, and all have served us well. Martin Martin was one of the top 2 center's in his draft class, and Brandon Thomas was projected to go first round before his injury. That makes for a pretty high-round heavy offensive line. Why slot in a random 4th/5th round pick? OL is the heart of the offense, and given how lousy ours was last year, improving it should be a goal. Much better chances of striking gold in the early rounds than the later rounds.
As for Justin Smith, it's looking more and more likely that he's not going anywhere. I seriously doubt he lets the team go into the draft thinking that he'll be here and then lets them know he's not coming back afterward. Dockett replaces RayMac, and he has 3 pro-bowl appearances, something that RayMac never had. IF Justin Smith retires, it's possible that a first round pick beats out Carradine for his spot, but I doubt it.
As far as MLB goes, all signs point to Bowman being ready to play, and Wilhoite is going to play next to Bowman. Wilhoite played for Bowman all last season and we still had a top 5 defense, so I don't know where people are getting the idea that we need an immediate replacement for Willis and Borland. Yeah, their loss hurt, but it's unlikely anyone is this draft is good enough to replace Wilhoite in that position, and no one is worth taking at 15.
And finally, WR. We have a couple of slow possession guys waiting in the wings to take over for Boldin (Ellington / Patton). Adding another WR would be nice, but unless one of the top 3 guys is available at our pick, it's more likely that we pick up another one after the first. WR is the only other place where I could imagine a top 3 WR coming in and starting as the WR3, but otherwise that role will probably go to Ellington.