Currently the series boasts ten teams, each running two cars, but that is set to increase with the arrival of another independent squad for the 2018/19 campaign.
Mercedes' specialist HWA has been linked to FE ever since the Silver Arrows signed its first option to join the electric single-seater category.
It has now been tipped to cement a deal to use Venturi powertrains in the 2018/19 campaign, a logical move given its current engineering tie-up with the team.
Any new FE entry had an initial deadline of Monday January 15 to register its intent to use a customer powertrain for next season.
The FIA will assess the entries before releasing a final list of teams later this year.
FE is not allowed more than 24 cars on the grid, which means if it grows to 11 teams next season one will need to disappear to make room for Mercedes and Porsche.
HWA had been expected to join next season to learn the category ahead of Mercedes' entry, and its absorption by the marque would easily take care of the numbers problem.
But some sources have indicated Mercedes way wish to operate an FE team itself instead.
This would raise the prospect of HWA competing in the category separately to Mercedes, given it will need a new racing focus after 2018 as its main programme is operating the six Mercedes-AMG C63s in the DTM.
Venturi is known to be considering aligning with another company long-term to boost its prospects against big-name, well-financed opposition, so collaborating again in the future would suit both parties.
Monegasque manufacturer Venturi will be one of nine powertrain constructors next season, with seven operating race teams and two making an independent their works operation.
Audi, Jaguar, Mahindra, NIO, Dragon, Nissan (which will take over Renault's homologation) and Venturi will field their own teams.
BMW's powertrain will be used by Andretti, while DS is poised to make Techeetah its manufacturer team in place of Virgin Racing, which has not ruled out continuing as a customer.
Virgin is understood to have agreed a powertrain supply deal with an unknown manufacturer ahead of Monday's deadline.