He would not get enough to get the nomination. About 1/3 of the states would not have him on the ballot. The deadline to get a party on the ballot is too soon.
He can simply run as the libertarian nominee and call himself the ‘Independent’ candidate. Libertarians already have access to the ballot.
Voters need not register as libertarians to nominate him if their state is an open primary state. Enough would crossover to ensure he’s on the ballot.
As for libertarian ideology, it doesn’t matter. The true adherents to that ideology are small in number. Their ballot access would conveniently serve as a vehicle to elevate Trump’s message.
And Trump could work his art on the libertarian brand as a solutions oriented political party. Ted Cruz could join him. The party’s bylaws could be utilized to change the name if necessary to ‘Independent Party’ etc.
And Trump has mentioned his admiration for some in the libertarian party.
The ‘Green Party’ also has national ballet access but their membership is another order of magnitude higher on the weirdness scale than libertarians. Their ideology follows the prevalence of their leftist members many of whom are hard-core left. So this would not be a match for Trump/Cruz.