While there is no doubt that San Diego could use an "elite" WR (heck, they could have used one even if they hadn't traded Boston), I do not think that they use their #1 pick for either Fitz or M. Williams.
The reason I think they pass is because they do not have the "delivery system" to take advantage of this skill set. Their offensive system is not WR friendly......a) they do not have a dominant pass protecting offensive line (with a GLARING, and I mean GLARING weakness at LOT) and b) they do not have the right QB to lead this type of an offense. Drafting one of the two elite WR's actually made more sense with Boston as they could have taken the focus off him alone defensively with another quality WR. Now that he's been traded, Fitz and or M. Williams would be in a "fishbowl" there.
They have a run focused offense geared around LT who can also be a pass catching threat out of the backfield when needed. They REALLY need to continue with this offensive strategy.......now is not the time to try and retool completely. IMHO, they need to think with the "big head" and if they do, they will bite the bullet and even though it's not the sexy pick, chose Gallery. He would provide instant results for a critical position of need.
I suppose they could take Eli (with tomorrow in mind). After all, they are certain to have a top three pick next year to use next year for one further piece to their offensive puzzle. Or they can trade out and go after multiple picks. Should they elect to go this route, whoever trades up, will not be after either of Fitz or Williams ( and we will not be a trade up candidate).
I do not see Marty having much influence on the draft personnel wise anyway. He's a lame duck who has been given the caretaker role until next year when they can go after their coach of the future.