Takeover talk, swirling around RIM for months, picked up steam on Monday as Heins took the helm at a once-dominant company that now struggles to compete. But RIM's shares tumbled more than 6 percent as investors wondered whether Heins could reverse RIM's decline.

RIM's co-CEOs Mike Lazaridis and Jim Balsillie finally bowed to investor pressure and resigned on Saturday. The looming presence of the two men who engineered RIM's rise has been seen as a big obstacle to a possible sale.

Even so, Heins said that option was not under consideration for now, and there was no need for drastic changes at the company, but rather a sharper focus on effective execution.

Shareholders and analysts have grown impatient in recent months and calls for Lazaridis and Balsillie to step aside have become louder. RIM has lost market share and market value after being comprehensively outplayed by the likes of Apple and Google.

"If Thorsten really believes that there are no changes to be made, he will be gone within 15 to 18 months. He will be a transitional CEO and this will be a transitional board," said Jaguar CEO Vic Alboini, who leads an informal group of 16 RIM shareholders calling for a radical restructuring. The group holds a little less than 10 percent of RIM's stock.

Lazaridis and Balsillie - two of RIM's three largest shareholders with more than 5 percent each - will remain board members, while Lazaridis will also head a newly created innovation committee. Their new roles suggest continuity was a goal in the transition.

Critics have called for a new leader that can rejuvenate both the design and operational sides of the business or prepare it for sale to one of a raft of rumored buyers.

Heins, who joined RIM in 2007 and previously served as a chief operating officer, said during a conference call on Monday that he would hone the current strategy rather than abandon it.

"I don't think that there is some drastic change needed. We are evolving ... but this is not a seismic change," Heins said.

Heins, a former Siemens AG executive, said that RIM, after its massive growth, needed to start operating like a mature business, not a startup.

INVESTORS DISAPPOINTED

"People may have been a little disheartened that he was defending the current RIM strategy," said Morgan Stanley analyst Ehud Gelblum. "I think (investors) might have wanted to hear a mea culpa."

"People would have been happier hearing 'we are on the wrong path'," he said. "We didn't hear a lot of talk about change."

Jaguar's Alboini criticized the retention of Balsillie and Lazaridis on RIM's board and called for several other board members to step down before the company's mid-year annual meeting.

"If we're wrong, prove us wrong," Alboini said in an interview, referring to the group of shareholders who support his view. "This group is not going anywhere. This is just putting RIM in a position where it might be able to get back into the game. It's early days."

Barbara Stymiest, a former banking and exchange executive, will replace Lazaridis and Balsillie as the chair of the board. Stymiest, who has served as a board member for five years, is also viewed as an insider tainted by association with the old regime.

LOOKING AHEAD

The new CEO's immediate concerns are to generate sales of RIM's current lineup of BlackBerry 7 touchscreen devices, deliver on a promised software upgrade for its PlayBook tablet computer by February, and rally RIM's troops to launch the next-generation BlackBerry 10 phones later this year.

But even if Heins had a credible overall plan to foster change, some analysts question whether RIM had fallen too far behind its competitors to catch up.

Its existing product lineup has struggled to compete with Apple's iPhone and iPad and the slew of large-screen and powerful devices from Samsung and other manufacturers using Google's Android operating system. In North America particularly, RIM has haemorrhaged market share during a year marked by product delays and a botched launch of the PlayBook.

"If RIM's going to grow in the U.S. ... they have to have products better than the iPhone or Android," said Pacific Crest analyst James Faucette. As of now, "they don't have products that are competitive with those, let alone better."

Analysts circled the calendars for an analyst day hosted by RIM in early May as the first opportunity for the new leader to lay out a detailed plan for reversing the decline.

The event "will now become the focal point to the unveiling of Thorsten's vision," CCS Insight analyst Ben Wood told Reuters. "The speed with which you make strategic changes and implement them is absolutely critical because the mobile phone business will not stand still."

"If there are no meaningful signs of an imminent turnaround, then I think the spotlight will turn back on to the assets that RIM holds and who they might be attractive to," he said.

NOKIA IN THE FRAME

In recent months, investors have seized on any rumor of a deal, whether with Amazon as reported by Reuters in December or with Samsung last week, as reason to celebrate.

Analysts have said that logical buyers for RIM also include fellow-struggler Nokia, perhaps with support from Microsoft, and Facebook which is increasingly pushing its content to users via their mobile phones.

If there is no obvious buyer, Heins has more immediate options to add value to the business.

RIM could license its software or integrate its email package, a strategy that many analysts and investors have thought the company might pursue. Heins said it would be wrong to focus on that option but he is still open to discussions.

"RIM have had big challenges in the past and they succeeded in moving from a corporate product to be also a consumer product, to get a foot in the consumer market and very few people expected them to do that," consultant John Strand said.

"Now they have to reinvent themselves again."

RIM's U.S.-listed shares fell 6.8 percent to $15.86.

(Additional reporting by Sinead Carew in New York; Writing by Andrea Hopkins; Editing by Andrew Callus and Frank McGurty)

• A Permanent Economic Emergency