Over the past few years BlackBerry (BB -3.02%) has been the subject of countless rumors ranging from the plausible to the truly ridiculous.

Years of mismanagement left the brand in disarray but with a small cadre of loyal users and a veritable legion of former customers nostalgic about the days when physical keyboards ruled. Like an aging, once-great athlete, many believers felt BlackBerry could be special again.

That has not happened, but the company has gained a measure of stability under CEO John Chen, who has, if not righted the ship, at least stopped it from taking on water.

"Our focus this past year was on getting our financial house in order while creating a multi-year growth strategy and investing in our product portfolio. We now have a very good handle on our margins, and our product roadmaps have been well received," Chen in a March press release on the company's fourth-quarter earnings. "The second half of our turnaround focuses on stabilization of revenue with sustainable profitability and cash generation." 

BlackBerry is no longer bleeding, and it has a plan for the future. That might make the company an attractive acquisition target for its latest rumored suitor, Microsoft (MSFT -0.32%). It's worth noting that neither company has commented on a possible deal, and at the moment it seems like something between a rumor and wishful thinking.

Still, while it might not actually be on the table, there are some strong reasons the acquisition would make sense. 

Keyboard phones targets business users
After a disastrous foray into attempting to compete with Apple's (AAPL -1.00%) iPhone, BlackBerry returned to its roots with a series of phones with physical keyboards. It even embraced its history by releasing the Classic, a phone that updates the company's traditional look and feel. That strategy should make the company more attractive to Microsoft, because the classic, keyboard-based BlackBerry was always popular with businesspeople.

BlackBerry's Classic. Source: BlackBerry

That is Microsoft's core audience, and while the company could develop a Windows 10 phone with a keyboard, that would not be nearly as appealing as one branded to BlackBerry. A phone with physical keys running Windows 10 but carrying the BlackBerry name might persuade a lot of lapsed fans to return to the fold. Add in the fact that Windows 10, with its universal app store, addresses the lack of apps that has plagued the company's phones and you might have a winner.

To make this happen, Microsoft would have to port all the signature BlackBerry features and apps into Windows, but that's certainly possible and it's not like any of the fondness for BlackBerry is tied to its OS. A Windows 10 take on the Classic would give business users a keyboard and access to the operating system they use at the office. 

Windows phone distribution channels are in place
BlackBerry has struggled with distribution for its new phones. Even the carriers it has deals with, including AT&T, do little to promote the devices. Joining Microsoft could change that -- the company has positioned Windows Phones as a lead player with T-Mobile and an at least somewhat prominent option with AT&T, Sprint, and Verizon

Windows Phones might not be all that popular, commanding only 2.7% of the market in the first quarter of 2015, according to IDC, but they are easy to find. Microsoft could bring that badly needed exposure to BlackBerry; both the Classic and the Passport (a keyboard phone shaped like a passport) created a lot of buzz, but were very hard to find at retail. 

BlackBerry can create great phones but it no longer has the partner support to have a hit. A deal with Microsoft could change that.

Source: IDC.

BlackBerry Messenger could be a signature app 
Since Satya Nadella took over as CEO, Microsoft has shown a willingness to port its signature products -- including Office -- to work outside of Windows. The company has stopped trying to force people into the Windows ecosystem, instead focusing on reaching as many users as possible even if that means finding them on iOS or Android devices.

BlackBerry Messenger, which has iOS and Android versions, could be another signature service that expands Microsoft's reach outside of the Windows universe. Owning BBM would give Microsoft something it currently lacks: an answer to Facebook Messenger, WhatsApp (also owned by Facebook), Twitter, and other messaging networks. The company could tie the chat app into Windows 10 on desktops, laptops, and phones, giving it a user base from launch in the same way Facebook did with Messenger.

Microsoft already has Skype, but that service is branded toward video and audio. BlackBerry Messenger could complement those well, giving the company a suite of communications apps that work across every OS.

Where there is smoke there could be fire
Microsoft has struggled with its acquisition of Nokia's smartphone business, but that should not stop it from making a deal here. While the Nokia deal has not been in a home run, Windows Phone would be in a much worse position had it not happened.

A deal for BlackBerry brings not only the three benefits mentioned above, but the company's parent portfolio and its work in the auto industry, which could complement Microsoft's growing efforts in that area. 

Chen has done a good job keeping BlackBerry alive, and he deserves credit for making the company worth buying. Now, for BlackBerry to grow, it needs to get bigger, and Microsoft seems like a very logical match.