Only if you deliberately ignore all the obvious downsides staring you in the face. It's like saying
1. I am tired
2. One is not tired when dead
3. Shoot myself
There is definite logic there as well by your standards
The logic is there but you are right all parameters have to be considered.
I would build a multi-year model with variables for:
1. Each manufacturer's expected relative performance for a given year.
2. Any performance discount as a customer relative to a works team.
3. Direct cashflow from Honda as a result of the works deal.
4. Cashflow(+/-) from a customer PU supply. Some positive cashflow possible by selling naming rights--like Redbull.
5. Expected cashflow from prize money--tied to performance
6. Expected cashflow from sponsors--tied to performance
7. Contractual impact of Honda leaving early--cash payout?
8. Contractual impact of McLaren leaving Honda partnership--cash penalty?
The big decision points would be:
1. The size of the cash input from Honda
2. How easy it is (likelihood) for Honda to walk away
3. Expected future cashflow lost from continued underperformance.
Everything is ultimately tied to Honda's expected PU performance in the future.
The model would allow variables to be changed so that you can arrive at expected financial impact of choosing an engine provider.
To me the biggest question would be if Honda can achieve top two status. If not it would be hard/impossible for them to beat:
Renault (within a year or two)
This would leave 5th and below up for grabs. Zak has already admitted that McLaren has a 100m budget gap (that's with Honda cash)--so unless there is an equal or better PU it will hard to see how McLaren out develops the aforementioned top 4 to break into that pack.
All that is to say that; choosing an alternative engine provider is not a logical fallacy.
I will put it to you like this, if McLaren could have a do over, which person would argue that they should have left Mercedes to go to Honda?
Within, the next 5 to 10 years the McLaren Honda partnership will be a case taught in business school. Everyone will then be a genius in hindsight.