How's this for a great movie idea: There's this streetwise, unconventional black cop from Detroit, see, and he goes to London on what's supposed to be a vacation. But once he's there he can't stop poking his nose where it doesn't belong, and pretty soon he's all mixed up in a case the local constabulary would just as soon pursue on its own. Naturally, his aggressive, throw-out-the-rule-book style is in direct conflict with the more civilized London bobbies, so all sorts of amusing problems result . . .

Sound familiar? That's the idea -- the scenario has been proposed for "Beverly Hills Cop II." No deal has been set, and Eddie Murphy hasn't agreed to appear in a follow-up, but last Friday producers Don Simpson and Jerry Bruckheimer discussed the idea with Murphy's manager, Bob Wachs, and said that Murphy is agreeable if a quality script is submitted . . . Eddie Murphy Productions, incidentally, just moved into new offices on the Paramount lot -- the offices formerly occupied by Sylvester Stallone, who, you might remember, was supposed to star as a hard-nosed Detroit policeman in a movie called "Beverly Hills Cop" . . .

Meanwhile, that film has now passed the $100 million mark in box-office grosses. It averaged $3 million a day for its first five weeks of release.

The next six films on the charts -- "City Heat," "Protocol," "2010," "Micki & Maude," "Pinocchio" and "Starman" -- all made about $1 million a day last weekend, which isn't headline news but isn't bad considering the traditional post-holiday drop-off in movie attendance . . .

"Beverly Hills Cop" notwithstanding, Paramount wasn't able to overcome Warner Bros.' pre-Christmas lead in the 1984 box-office totals. Though Paramount gained ground quickly for the last month, Warner Bros. squeaked by, picking up a 19.4 percent share of the year's domestic market to Paramount's 19.1 percent. Elsewhere in the industry, "Ghostbusters" helped Columbia engineer a decisive turnaround. The studio's 15.1 percent year-end share was double its June total, and well above anything it's seen since the days of "Tootsie." These figures, however, are total gross -- a more accurate indication of profit is total film rentals, a studio's shares after paying distributors and exhibitors. Those figures haven't been released yet, although Daily Variety has disclosed that on that scale, Paramount comes out on top . . .

The Academy Award sweepstakes is getting as muddy as Mel Gibson and Sissy Spacek's back yard in "The River," especially now that the National Association of Film Critics has chosen Jim Jarmusch's offbeat "Stranger Than Paradise" as the year's best film. If it had gone with either "Amadeus" or "A Passage to India" -- picked by the Los Angeles and New York critics, respectively -- it could have started the kind of groundswell that results in an Oscar favorite. But when that normally conservative body chose a low-budget, stylized, deadpan comedy that will almost surely get no recognition from the Academy, it increased the confusion of a year in which Oscar nominations are more in doubt than any in memory . . .

The Golden Globe nominations, which aren't taken very seriously, did indicate that "Amadeus," "A Passage to India" and probably "The Killing Fields" are on reasonably strong footing for nominations. But after that, what? "A Soldier's Story," or will "Killing Fields" take the serious-military-movie vote? "Places in the Heart," or will "Country" and "The River" split the farm-movie vote? Steve Martin for "All of Me," or will the Academy ignore his two critics' awards and Golden Globe nomination in favor of its longstanding preference for serious performances? This year, voters have 228 eligible films to choose from, up from 223 last year. Stay tuned -- nominations will be announced Feb. 6 . . .

One last "Cotton Club" story, and then we'll stop, honest: In one of the strangest deals on record, actress Susan Mechsner, who appears in a single scene as a cigarette girl, was paid $100,000 and given two percentage points of the film's profits. It seems that Mechsner was at a cocktail party, where she made some introductions that resulted in producer Bob Evans meeting financiers Ed and Fred Doumani. One of her profit points was a gift from Evans, while the other came from an anonymous major investor. As for her big salary, it apparently came about because her role was originally bigger and was either cut by director Francis Coppola (Mechsner's story) or shortened when she was injured after four days' work (Evans' story). Mechsner says she's going to sue over the trims in her role. And, in a final bit of indignity, the film's credits misspell her name . . .