There are inventors who hope to pay the government fees for a patent only after their inventions are sold out.
There are inventors who are individuals and could not afford the high amount of the government fees although there are some discounts or tradeoffs.
Yet the government bureau often revokes a patent application or a patent and bring an end to the applicant or patentee. This is too strict a rule which has ruled out many inventors' dreams.
Once the law will make some slight modifications, things might be quite different.

If a patent application is filed and the filing fees are paid, it could be revoked but not terminated within the period of its life, say, 10 or 20 years from the filing date.
If a patent is granted, it could be revoked but not terminated.
In turn, the appicant or patentee should give a step back. His intellectual rights are not protected during the period being revoked. Anyone may utilize the invention during that period without paying the roylty fees at any time.

For example, if an inventor has filed an application and paid the filing fees, but he failed to pay the annual fees for 3 years, then the application is revoked, anyone may utilize the invention freely during those 3 years and do not have to pay anything even after the patent is granted.
If the inventor has sold out his invention during the 7th annual period, he may ask for an eaxamination and pay the examination fees plus the 7th annual fees. And the 7th annual period shall be protected.
Same for a patent granted.
If the patent tends to not sell well during the 9th annual period, the patentee may not pay the 9th annual fees and the patent is not protected during the 9th annual period.
If a patent tends to sell well during the 10th annual period, the patentee may pay the 10th annual fees and the patent is protected during the 10th annual period.

For a PCT application, things are somewhat different. If a national application is filed and the filing fees paid, the applicant may file a PCT at anytime and enter the national phase of a country at anytime. He may wait until he has sold out his invention.

All these modifications should be in effect for the past patent applications or patents. Because many inventors have been obliged to give up their rights plus their dreams. The laws revised should give them a chance to take the advantage of their inventions.