If your plan is to rely on the court system, then just rely on the court system. You can write your contract on paper; smart contracts serve no purpose whatsoever then.
But just as in real life, an executor can make mistakes.
Traditionally, a judge may return or redistribute assets in such a case. Or claim the will was not interpreted correctly. In such cases, determining the intent of the contract is the goal of the court.
Like it or not, smart contracts are not immune to contract law, civil law, courts.
The first court cases, which will undoubtedly happen, will be very interesting.
And moreso, different legal jurisdictions will interpret things differently. If I was writing smart contracts, I'd want some sort of boilerplate, insisting upon legal jurisdiction, maybe like an open source license, but for smart contracts.
After all, once your identity is known, normal courts can compel you to do things...
Intent is certainly a big part of law.
When examining classic contracts, a judge will try to also deem intent.
Contracts have been thrown out, interpreted by intent of parties.
An example, are the comments in the source code for this smart contract? Did everyone have opportunity to see them?
It could affect a court battle...