In many of these examples, there are just two forms of the same word being used, the verb and noun; or in the case of invalid, the adjective and the noun.

With the unrelated pairs, spelling reform could be introduced. For example lead, the verb, could be spelled "leed" and lead, the noun, could remain "lead". Or a simplified phonetic alphabet could be introduced that could be used to spell all words strictly based on their pronunciation (lead, the verb = \lēd\; lead, the noun - \led\). But not everyone agrees on the pronunciations of all words.

Two other changes that would improve the English language are:

1) Elimination of the "-s" or "-es" on third-person singular present tense verb forms (he runs, he goes, etc).

2) Changing most verbs to the regular "-ed" form (go/goed/goed, fly/flied/flied, etc). The verb be and non-changing verbs such as put, hit, cut, etc. could remain the same, for old time's sake and convenience.