As Disney's (DIS 0.16%) Marvel Cinematic Universe expands, one burning question is whether there will ever be a new solo film for the Hulk.

Actor Mark Ruffalo, who portrayed the Hulk in The Avengers, has confirmed Marvel has been considering a new Hulk solo film. Marvel Studios President Kevin Feige has also mentioned some ideas for the film before, including the popular Planet Hulk and World War Hulk comic book storylines, but nothing has been greenlit so far.

Source: Marvel.

Out of all the main Avengers characters, the Hulk has had the toughest time on the big screen, after two prior films struggled with balancing out Bruce Banner's relationship with his big green alter ego. Despite these issues, Marvel should still make a new solo Hulk film soon for three major reasons.

1. The Hulk is still a profitable beast
The first two Hulk films (Hulk, 2003 and The Incredible Hulk, 2008) were produced by Comcast's (CMCSA 1.57%) Universal Studios. Both films were profitable -- the first film grossed $245 million on a budget of $137 million, while its sequel grossed $263 million on a budget of $150 million. Neither film bombed with critics -- the first film earned a 62% rating at Rotten Tomatoes while the sequel fared slightly better at 67%.

Yet despite the decent commercial and critical reception, both films fell flat with fans of the comic and the campy TV show. In the first film, director Ang Lee replaced the pulp factor with a deathly serious examination of Banner's psyche. Louis Leterrier's sequel, a narrative continuation of the first film, delivered better sequences of the Hulk smashing things, but it felt just as glum as its predecessor.

In 2006, Marvel regained the rights to the Hulk, and recast Mark Ruffalo as the Hulk in The Avengers. Unfortunately, Marvel seems unsure about how to proceed. The two storylines Feige mentioned -- Planet Hulk and World War Hulk -- wouldn't make sense as solo films, since the former stars the Hulk fighting in a gladiatorial arena on an alien world, while the latter turns Hulk into an enemy of the Avengers.

World War Hulk. Source: Marvel.

What Marvel should do is bring back director Edgar Wright, who left Ant-Man in May due to creative differences with the studio. His manic, comedic filmmaking style, as seen in The World's End and Shaun of the Dead, would be a perfect fit for a new solo film starring the Hulk.

2. Phase 3 needs a stronger opening
Ant-Man, which is now being directed by Yes Man director Peyton Reed, could have a tough time at the box office. Optimists think that Paul Rudd's sarcastic charm can carry the film, but pessimists think that the character's lack of mainstream recognition could hurt the franchise's chances of success. If Ant-Man bombs, it could derail subsequent Phase 3 films starring lesser-known characters, such as Dr. Strange.

In my opinion, a solo Hulk film, co-starring Ant-Man, could be the perfect launch title for Phase 3 following Avengers: Age of Ultron. Ant-Man would be the perfect adversary or partner for Hulk in a stand-alone film, since Ant-Man can transform into Giant-Man, a formidable physical match for Hulk, while still retaining his wits.

Would Hulk vs. Ant-Man be a better launch film for Phase 3? Source: Marvel.

Therefore, delaying Ant-Man's release in favor of a new solo Hulk film would be a more ideal opening to Phase 3.

3. Looking beyond Iron Man and Captain America
As we look beyond 2016, we see two other big problems -- the fact that Iron Man (Robert Downey, Jr.) and Captain America (Chris Evans) could leave the Marvel universe.

Downey, who will turn 50 before Avengers: Age of Ultron is released in May 2015, has hinted that the film could be the last time he portrays Tony Stark. Downey's departure would hurt the future of Iron Man, but it could also resolve major pay disputes among the cast. Downey was reportedly paid $50 million for the first Avengers film (23% of the film's production budget), while other cast members were paid as little as $200,000. Mark Ruffalo's salary was estimated to be around $3 million.

Evans is signed on for three more films beyond Captain America: Winter Soldier (Avengers: Age of Ultron, Captain America 3, and an unknown project), but there are persistent rumors that Steve Rogers could be killed off in Captain America 3 and replaced by the Winter Soldier, Bucky Barnes (Sebastian Stan).

The Winter Soldier. Source: Marvel.

Therefore, a solo Hulk film series could offset the risks that Marvel faces with future installments of Iron Man and Captain America, as well as with lesser-known series like Guardians of the Galaxy, Ant-Man, and Doctor Strange.

The Foolish takeaway
Marvel is understandably reluctant to take the plunge with a new Hulk film, especially when the last two films failed to generate box office returns on par with solo films starring Thor, Iron Man, or Captain America.

But I believe with the right writer, director, and cast, the Hulk could emerge as a new pillar of growth for Disney's Studio Entertainment segment, which accounts for roughly 15% of its top line and 14% of its bottom line.

So what do you think, fellow comic book film fans? Is it time to finally time for Marvel to give the green light to the green giant? Let me know in the comments section below!