If you don't want to negotiate that contract, the majority of the market will come together and refuse doing business with you until you do.
The unions negotiate for "All workers" under some kind of umbrella terms that has only sometimes specific prescriptions towards individual companies but always towards industries as a whole. They can dictate things like medical, vision, dental, sometimes day care. But they can also dictate things like work hours, safety, etc.
That all sounds gravy, but what if a company like Tesla wants to dictate 60 hour work weeks for all it's engineers. But that goes against Union Law, so they can't. But what if that's just how the people in the company, and people within that company want to work. That's how Tesla works. When you are getting of job at Tesla, you know exactly that you are signing up for long work hours. It's a company with everyone putting in 70 hour weeks for around 2 years, and springboard into another startup at a higher role, or more cushy FANG.
To give another example from another industry that would not work is the oil fields. We have the OCAW union here in the US but get like 1/4 of what the non-union jobs get. Because OCAW dictates work hours, and a salary but not time to rig. the non-unionized guys go out and work for 18 hours straight, sleep on a the rig for a bit, and get back to work. Again, not allowed under union contract, but if you do that for a couple days and make a bunch of money. Because we have worker pay, OSHA, etc. There is no need for unions here because the minimum labor standards for overtime pay and safety are set by federal standards not the "Union".
"Collective Bargaining" has lost it's sense of "Collective" at the scale it has grown. True collective bargaining has always been by the individuals themselves. Forcing Tesla on a blanket union contract instead specific clauses and prescriptions that they need to implement to be compliant is legalease non-sense.
Which is exactly why the choice to handle the labor market under contract law has been made.
If Tesla wants to dictate 60 hour work weeks for engineers, they negotiate a new contract with the relevant union. That's why engineers have their own union, to gain the flexibility to negotiate contracts localized for specific sectors and part of the workforce.
Now 60 hours a week is a lot. That's not good example since it so extreme there is likely no legislative room for that. It is 12 hours a day and society would simply not be prepared with daycare and other amenities. Even if it was legal it would not be good for families and cause increased healthcare costs. Maybe you could argue for some sort of nanny system but nobody pines for the 19th century bourgeoisie anymore. Too much is known from that era.
> Forcing Tesla on a blanket union contract instead specific clauses and prescriptions
Yes, this is exactly why Telsa needs to negotiate a contract.
You seem to advocate for the model which exactly what is already used. Tesla needs to negotiate a specific contract for them, instead of relying on blanket labor law.
There is no legislation that requires this, which is the case in for example neighboring Finland. This is to accommodate for smaller businesses where contract negotiation is an unnecessary burden. There are pros and cons with both models, but it is important to realize how this is different from for example the German model.
The choice has been made and the labor market is handled with contract law. You can argue that that is a bad idea and Sweden needs to adopt the French or American labor market model instead. That's would be intellectually honest. You could also argue that there should be stronger laws against operating without labor contracts, like in Finland. Which is also fine.
But you can't argue that Tesla should be allowed to operate without a specific contract, when the circumstances clearly demand one. That's at best a misunderstanding and at worst just dishonest.