Don't force all industries to close inside town. Some may stay. A reduced raw material storage capacity would make it harder to feed an industry within the city, or better the industry could shut down periodically (for a month or more) as a penalty from city council because it pollutes. I don't know if these are easy to implement. If you believe that they should close make it s that it takes 1 to 2 years and not 6 months.
that is easy
Scenario editor should be free from restrictions as we may want to create real life conditions.
From all restrictions? This point should be discussed first, be cause I do not like it. What conditions are hard for you in the editor?
Who else thinks the same?
Workers can take the train/bus to go to their work. Hmmm, need I say I 'd like to see industries accept passengers like in Simutrans?
it is easy to make them accept passengers. But it is impossible to make industries to produce passengers or to make passengers affect production (for industries which have 3 input and 2 output already).
Theoretically coders could provide a new callback for industry tiles, so they could produce cargo as houses do (themselves, independently form the industry), but you should ask coders.
About transforming industries: Our former gas factory has been transformed into an "artcity" (industrial museum, concerts, etc.)
I didn't say it is impossible IRL. I said that I do not find it is useful in [O]TTD[P]. It requires much work but gives the same behaviour as a group of houses, placed instead of the industry.