Unfortunately, this ship sailed quite some time ago. For example, after the 2008 financial crisis, the Senate rejected a proposed bailout of GM. But Bush approved it anyway:
https://en.wikipedia.org/wiki/Effects_of_the_2008%E2%80%9320...> However, it had been argued that the Treasury lacked the statutory authority to direct TARP funds to the automakers, since TARP is limited to "financial institutions" under Section 102 of the TARP. It was also argued that providing TARP funds to automaker's financing operations, such as GMAC, runs counter to the intent of Congress for limiting TARP funds to true "financial institutions".[79] On December 19, 2008, President Bush used his executive authority to declare that TARP funds may be spent on any program he personally deems necessary to avert the financial crisis, and declared Section 102 to be nonbinding.
Also, “unitary executive” doesn’t mean overriding other branches. It just means that whatever powers the executive branch does or does not have are exercised by the President, just like the 535 members of Congress exercise all the powers of Congress, and the 9 Justices exercise all of the powers of the Supreme Court. It means that executive branch employees don’t have independent powers, just as House staffers and Supreme Court law clerks don’t have independent powers.
See: https://en.wikipedia.org/wiki/Federalist_No._70 (“Federalist No. 70 emphasizes the unitary structure of the executive. The strong executive must be unitary, Hamilton says, because ‘unity is conducive to energy...[d]ecision, activity, secrecy, and dispatch will generally characterize the proceedings of one man in a much more eminent degree than the proceedings of any greater number.’”).