How about the salaries of employees being paid to create a new line of business? Say, the business runs restaurants and you decide to break into the tax software business. Can you avoid taxes on restaurant profits right now in order to build your new unrelated venture. ISFICR, tax law allowed outright deducting of costs of the current business, but not costs for starting a new one. Not deducting the new costs against the old profits.
After that, we can nitpick: should the development costs of new software be encouraged the same as maintenance costs of existing software. If you want to encourage startups, then yes they should. If you want to discourage startups or very temporarily increase tax collection, then no.
Discouraging starting new businesses would be unconstitutional. All freedom in the US is derived from being able to participate in controlling capital.
After that, we can nitpick: should the development costs of new software be encouraged the same as maintenance costs of existing software. If you want to encourage startups, then yes they should. If you want to discourage startups or very temporarily increase tax collection, then no.