I absolutely agree that Briggs has not earned a shot at the title.
That being said, boxing is structured in a way where a champion has to make mandatory defenses - which Wlad just fulfilled by KOing his mandatory Pulev - but he is also granted voluntary defenses against an opponent of his choosing (provided the opponent is OK'd by the sanctioning bodies, usually means he needs a decent ranking within said bodies). Typically, the "opponent of his choosing" will be the opponent who would command the most public interest, most money, or has some sort of grudge with the champion.
I think Klitschko-Briggs would make for an entertaining fight while it lasts. It would be fun to watch, just imagine the weighin lol. And after their confrontations, it might be a good for the casual boxing fans that this fight happens.
Besides, it's not like Wladimir has many other options, consider the Top-10 at HW according to Boxrec;
2 - Povetkin (already beaten by Wlad)
3 - Pulev (already beaten by Wlad)
4 - Stiverne (unavailable till Summer 2015 or later)
5 - Glazkov
6 - Chisora (fight VS Fury very soon)
7 - Jennings
8 - Solis (recently lost to Tony Thompson, a Wlad KO victim, fight makes no sense)
9 - Wilder (unavailable till Summer 2015 or later)
10 - Hammer (is inexperienced and has little power, would be a huge mismatch VS Wlad, fight makes no sense)
Wlad's manager Bernd Boente has discussed Bryant Jennings, Shannon Briggs, and Fury-Chisora winner as possible next opponents. Honestly, Jennings would get destroyed and he doesnt bring anything to the table more than Briggs in fact Jennings brings less because atleast Briggs had a famous name at one point.
Tyson Fury is a credible title challenger at heavyweight, and I'm a huge fan of him, but quite frankly I'm not even sure that Fury wants the fight. He's called Wlad out in the past but when push comes to shove he doesnt seem to want the fight. He may instead wish to target Stiverne/Wilder winner. I dont know.
There's also been some talk of Bosniak Muamer Hukic (Marco Huck) coming up to heavyweight and fighting Wlad, but I think it's all talk at this point and Huck would be facing a huge size disadvantage. I have to admit it would be an interesting fight though...
As a final point, Briggs will not make that much for the fight. He'll get a generous 1Mill or so (typical of all Wlad opponents) while Wlad will do the lion's share 10Mill or so. The purse split would be 90-10, maybe even 95-5.