So much dust has been raised concerning the letter transmitted to the National Assembly by the President empowering VP to COORDINATE or to perform in ACTING capacity in his absence. What is sacrosanct is the constitution which both the President and Vice President derive their functions and powers to act from.
The letter made reference to section 145 (1) as amended which states.

"Whenever the President transmits to
the President of the Senate and the
Speaker of the House of Representatives
a written declaration that he is
proceeding on vacation or that he is
otherwise unable to discharge the
functions of his office, until he transmits
to them a written declaration to the
contrary such functions shall be
discharged by the Vice-President as
Acting President."

The President by the transmission of the letter to the National Assembly notifying them of his leave, triggers that section. The wordings of the letter does NOT invalidate or reduce the power of the Vice President to act in ACTING capacity. The wordings of the President's letter cannot reduce the VP's powers to act in ACTING capacity as the section of the constitution triggered, supersedes the wordings of the latter.

If even the choice of words COORDINATE THE AFFAIRS OF GOVERNMENT is a cause for concern, section 148 (2) (b) empowers the President or Vice President to coordinate the affairs of Government as as stated below.
148. (1) The President may, in his
discretion, assign to the Vice-President or
any Minister of the Government of the
Federation responsibility for any business
of the Government of the Federation,
including the administration of any
department of government.
(2) The President shall hold regular
meetings with the Vice-President and
all the Ministers of the Government
of the Federation for the purposes of
-
(a) determining the general
direction of domestic and foreign
policies of the Government of the
Federation;
(b) CO-ORDINATING the activities of the President, the Vice-President
and the Ministers of the
Government of the Federation in
the discharge of their executive
responsibilities;

The word coordinate is constitutionally CORRECT.
The President it seems is more knowledgeable about constitutional provisions than those causing mischief out of malice or sheer ignorance.
My deductions from the whole issue is that
1. THE PRESIDENT'S LETTER TRIGGERED THE SECTION OF THE CONSTITUTION THAT EMPOWERS THE VICE PRESIDENT TO PERFORM IN ACTING CAPACITY.
2. SECTION 148 (2) (b) EMPOWERS THE VICE PRESIDENT TO "COORDINATE" THE AFFAIRS OF GOVERNMENT AS STATED IN THE PRESIDENT'S LETTER AND AS ENSHRINED IN THE CONSTITUTION.