Line Interpretation...

[KuroKyosuke]

行動が変してゆきます。 - koudou ga hen shite yuki masu.

I've translated this line as "[Their] actions will change".
I was wondering, could this also be interpreted as "[Their] actions will become strange"?

[Datenshi]

I was wondering, could this also be interpreted as "[Their] actions will become strange"?

In a word, no. If you translate 変 here as [strange], 変してゆく would literally translate as "go strange", which makes no sense. If it meant that, it would read 変になる (変になってゆく).

[mopuis]

Since there is no verb like 変する in Japanese,
I'd assume "化" is dropped out between "変" and "してゆきます".

The sentence must be "行動が変化してゆきます" ,
meaning "[their] actions will change " , just as you translated.