By Ulf Laessing and Alexis Akwagyiram
LAGOS (Reuters) - The window for Yemi Osinbajo, Nigeria's stand-in president, to launch bold economic reforms and wrestle the ill-disciplined naira currency into shape is fast closing.
President Muhammadu Buhari signaled over the past weekend that he is ready to return from receiving medical treatment in London as soon as his doctors allowed it.
That would could paid to investor hopes for economic changes to qualify Nigeria for a World Bank loan to drag it out of recession. It will also leave the plethora of naira exchange rates standing, albeit perhaps closer to each other.
Buhari has kept a grip on power despite his medical leave, and the more business-friendly Osinbajo has been reluctant to challenge him.
This has gone as far as him flying to London to get permission for personnel changes.
"We don't expect any deviation from the current economic policy stance should President Buhari return," said Cobus de Hart, senior economist at South Africa's NKC African Economics.
"One could hope that the return of the president goes hand in hand with an acceleration of reform implementation, but we doubt this will be the case."
Osinbajo, who has been running Nigeria since Buhari went to Britain on May 7 and also ran it between January and March, has made some changes.
He has managed to calm tensions in the Niger Delta oil hub and pushed small steps such as a forex trade window to narrow the gap between the official and parallel naira exchange rates.
But a unifying of all the exchange rates -- there are at least six, including the black market -- remains far away. It would amount to a devaluation, which Buhari has opposed.
More than three months after leaving Nigeria, it remains unclear when Buhari will return, despite his remarks about his desire to resume work. They were merely the latest in a number of presidency announcements.
But even from far-away London Buhari and his aides have restrained Osinbajo.
"He (Osinbajo) is so scared to offend President Buhari to the extent that he takes no major action without consent from him through phone," said a presidency official, asking not to be named.
Osinbajo and his aides often hold meetings which has enlivened a presidential villa criticized for inertia -- but he still seeks approval from Buhari or his chief of staff.
He flew to London for a few hours last month to get Buhari's approval to appoint two ministers who had been already cleared by parliament, the official said.
During the meeting, Buhari even asked Osinbajo to give the ministers no portfolio as he wanted to assign them himself after his return, he said.
Moreover, when Osinbajo tried appointed a new board for an anti-corruption commission he had to withdraw his candidates because Buhari's aides did not like two names, the official said.
Among the few projects Osinbajo got underway are the legalizing of illicit refineries in the restive Niger Delta oil hub, often the only work for youth who tend to join otherwise militants.
Osinbajo also ordered an overhaul of dilapidated facilities at Lagos airport, the main entry gate into Nigeria, as part of a plan to ease doing business.
The new FX trade window has prompted some foreign investors to return, pushing Nigerian stocks to a nearly three-year-high in August.
But its inconclusive nature still holds back investors, London-based Capital Economics said.
"There is a possibility that Buhari returns, sees things improving and thinks there is no need to change anything. Further reforms are desperately needed to achieve meaningful growth," said John Ashbourne, Africa economist at Capital Economics.
Buhari, a former military ruler from the north, made Osinbajo acting president when he first went to Britain to avoid a vacuum as occurred in 2010 when then-President Umaru Yar'Adua spent three months in a Saudi hospital while his aides shrouded his illness in secrecy.
His deputy Goodluck Jonathan only took over in a constitutional crisis after Yar'Adua died.
Osinbajo has gone out of his way to show his loyalty -- as a Christian lawyer from southern commercial capital Lagos he is walking a tightrope to avoid policies that may annoy Buhari and his inner circle, who are mainly Muslim northerners.
"The chief of staff and his team are working alongside Osinbajo on the understanding that (he) will not run in 2019," a government adviser said. Osinbajo has never said he wants to run.
"The election cycle is the last two years of an administration. As we enter the election the issue of mutual trust becomes crucial because nobody wants to be ambushed," said the adviser, who did not want to be named.
Traditionally in Nigeria, the leadership rotates between north and south to ensure a balance in a country evenly split between Muslims and Christians.
Jonathan, a Christian from the south, upset many northerners by refusing to give way. Northerners also felt there should have been another northern term after Yar'Adua's death. Hundreds were killed in riots after Jonathan's election in 2011.
(Reporting by Ulf Laessing and Alexis Akwagyiram Additional reporting by Paul Carsten in Abuja; Editing by Jeremy Gaunt)