Not sure about "theoretical grammatical correctness", but in practice only a small handful of combinations are used / will make sense; you can't just slap verbs together willy-nilly.
There are two cases to consider here:
Verbs that can be used as an auxiliary suffix. These can be attached to pretty much any other verb, and modify the first verb's meaning. ～続ける means "to continue doing ～", ～出す means "to start doing ～", ～合う (note: not 会う) means "to do ～ to each other", etc. Jisho usually tells you when a verb can be used like this.
Set compounds. Here, rather than the latter verb modifying the former in an A[B] manner, you've just got an A+B compound. 見失う exists, and its meaning emerges as a combination of 見る's and 失う's, but ～失う isn't used as a general auxiliary.