The phrase "arguably unnecessary" is correct and usable in written English.
It can be used when discussing something that may not be essential or required, but there is room for debate about its necessity.
Example: "The additional features in the software update are arguably unnecessary, as most users prefer a simpler interface."
Alternatives: "possibly redundant" or "potentially superfluous".
All this environmentally unsound galumphing around the globe is arguably unnecessary in the age of live streaming.
Most importantly, he was guilty of an arguably unnecessary intervention that led to the first Scottish sin-binning, a decision which really cost his side.
The fiscal cliff proposal that led to Mr. Boehner's Plan B was full of significant, arguably unnecessary concessions that the Republicans predictably ignored.
The ever-elusive Kate Bush ended a six-year hiatus with not one but two albums: the enjoyable but arguably unnecessary reworkings of her old material on Director's Cut and the wonderfully wintry 50 Words for Snow.
In 2009, drugs company BioMarin took it upon themselves to produce a similar but arguably unnecessary replacement drug, which they said was more stable and reliable, and charged up to 70 times more than the original.
For instance, part of the Navy's $16.1 billion shipbuilding budget for 2011 includes an extra $2.7 billion Virginia-class submarine, an arguably unnecessary expense in the post-cold war world.
IT WAS, said Michael McCurry, the president's genial spokesman, "arguably an unnecessary day in the life of our country, an awful day"; and this is a common response to Bill Clinton's video testimony.
The proposal "arguably involves unnecessary Europeanization of the supervision of a benchmark, the oversight of which has already been reformed by the U.K. authorities," said Barney Reynolds, a partner at the law firm Shearman & Sterling in London who advises clients on European and British financial regulation, referring to Libor.
Although there was no direct endorsement of tobacco brands, their presence in music videos is arguably entirely unnecessary and illegal under the 2002 Act [ 50].
The list will almost certainly hit nine after Raffi Torres of the Phoenix Coyotes propelled himself into Chicago's Marian Hossa for an arguably late, inarguably unnecessary check.
California's Supreme Court has arguably allowed for unnecessary litigation by its expansive view granting non-litigants standing to appear in cases such as this as intervenors.
