Before the Monaco Grand Prix, weekend Honda announced it would return to F1 as a fully-fledged engine manufacturer by supplying works power units to Aston Martin from 2026, when F1 moves to new engine regulations with a higher degree of electrification and sustainable fuels.
Honda is the last of the six manufacturers that registered for the new engine cycle to commit to a programme, which leaves McLaren, Williams, Haas and AlphaTauri without bespoke deals.
As Red Bull's secondary team, AlphaTauri will benefit from its parent squad's Ford tie-up, while Haas is inextricably linked with Ferrari through its technical partnership with Maranello.
That leaves Williams as one of the teams destined to remain a customer for the time being, with new team boss James Vowles exploring whether to remain with Mercedes or find a deal elsewhere.
Vowles acknowledged the first year of the new engine cycle "potentially becomes a little bit difficult" for customer teams to integrate the new power units into their chassis, but he believe customers can still be competitive if the regulations remain stable.
"I think the first get go into 2026, potentially there it becomes a little bit difficult," Vowles said. "But the learning will kick in shortly after that.
"I think what Aston has shown you is that you can take that and you can run with it, albeit Aston are going their own way. But I don't think it limits you necessarily in a stable set of regulations."
Vowles experienced both scenarios after coming over from Mercedes, which stole a march on the entire field in 2014 with its Brixworth-built engines the envy of the paddock in the turbo-hybrid era's early years.
He admitted there are obvious compromises for customer teams, but F1's stipulation to provide equal engines has allowed squads such as Aston Martin to be competitive, with Aston and Williams currently also taking Mercedes gearboxes to improve the engine integration.
Aston's split from Mercedes will coincide with setting up its own gearbox programme, a decision that Williams is yet to make.
"The closer you are linked with your engine manufacturer, the more you can do the lay-out of the back of the car the way you need it to be," Vowles explained.
"So, your compromise between aerodynamic cooling, performance versus power generation, that compromise can be set by yourself, and you understand all of the targets. Clearly in a relationship, and we are a customer with Mercedes, that's a lot more difficult.
"However, there are regulations in place now that are very good, that mean that the power unit we're being supplied is the same power unit as elsewhere. That wasn't the case many years ago. So I have confidence at least that the power it's generating is good."
Ferrari's Laurent Mekies, who will become AlphaTauri's team principal next year, doesn't believe a works deal will become any more important in 2026 than it is now, pointing at F1's efforts to drive the field closer together with a cost cap and less complex engine rules.
"Needless to say, with the amount of integration that there is between the chassis side and the power unit side, of course, it's always going to be an advantage," Mekies acknowledged.
"Does that stop you from operating at a very high level if you don't have one? Some people are proving that it's possible to do a very good job without that sort of deal, so I don't think it's going to be more important in the future than it is already today.
"I think the level of complexity of the power units is already sky high today and if anything, we are doing steps in the regulations to decrease that complexity tomorrow and, hopefully, it will give us an even more compact field."
