Shades of George C. Scott as Holmes with a female Dr. Watson in They Might Be Giants...1972, IIRC.
Think of him as a "lad", a bit more "street" than his ancestor. A bit more rough around the edges. Picture him, in fact, played by Vinnie Jones, of the movies Lock, Stock, and Two Smoking Barrels and Snatch.
Going for a straight clone of the old one would be a tad boring, IMHO. He'd have to fit in his new time frame and context. You could keep most of the old eccentricities, though, like the pipe and such, and his laboratory. He'd be just as intelligent and driven, but more comfortable moving about in the modern underworlds.
As for Watson, I am adamant that she NOT be some young knockout. Her role would be best served by a middle-aged, proper lady, one offering a marked contrast to the younger, tougher Holmes. I HATE it when lazy writers set up an obvious romance, and one should not be here. I'd picture her as resembling James Bond's Miss Moneypenny in looks and demeanor, if not in her crush on her friend.
SCENE: Tony, seated at a table in an otherwise empty pub, has three goons pointing pistols at him and demanding his surrender. He just keeps at his pint and says...
"The fact that you've got "Replica" written down the side of your gun. (draws his own gun) And the fact that I've got "Desert Eagle point five O" written on the side of mine, should precipitate your ba**s into shrinking, along with your presence. Now... F**k off!"
It's a classic.