One alternative word that can be used instead of "they" is "them."
Another word or phrase that can be used instead of "for this reason" is "therefore" or "as a result".
Substitute or exchange can be used instead of replace.
The term for using one word instead of another but conveying the same meaning is "synonym."
Some alternative words that can be used instead of "introduced" are: presented, unveiled, initiated, or launched.
Tone, sound, or expression can be used instead of voice in some contexts.
instead of being that
no "It" is not used instead of he and she...
used to be
How come is often used instead of why.
But may be used - instead of however, in most contexts.
unserrated
herbage
an word that can be used instead of pen
pronoun
effective.
In the King James version the word - instead - appears 39 times
Another word or phrase that can be used instead of "for this reason" is "therefore" or "as a result".