> That is probably the most common structure for a language. Swahili verbs are entirely regular and can have a long sequence of prefixes which follow a strict order.
This seems a little confused. If a language's verbs are entirely regular, the normal point of view would be that that language doesn't inflect verbs at all.
For example, an English verb can include up to four prefixes, which occur in an order that never changes and which do not depend on the verb. In this sense, that part of the grammar is "fully regular". (Note that all of these prefixes are verbs, and with the exception of the first set, they inflect like verbs. The first set inflect only for past tense.)
[Those prefixes, in order, indicate: modality (there are many verbs that can occupy this space, but they're all mutually exclusive with each other), perfect aspect (exactly one verb can occur here), continuous aspect (again, exactly one verb can occur here), passive voice (two verbs, mutually exclusive). Any of the sixteen theoretical combinations of these is allowed.]
But that's all periphrasis. English verbal inflection is a different phenomenon: each verb has five forms (except be, which is special and has more): plain (take), past (took), third-person present singular (takes), active participle (taking), and passive participle (taken). This is where a verb might be irregular or not. A regular verb's past form adds the suffix /d/ to the plain form, the active participle adds /ɪŋ/, the third-person present singular form adds /z/, and the passive participle is identical with the past form.
All verbs are regular in their active participle and only be is irregular in the third-person present singular.† But verbs might have arbitrary past forms (go / went) and while the passive participles are never arbitrary, there is a set of irregular forms following a common pattern that descends from an earlier stage of the language. (taken / been / gone / known / gotten / ...).
There is a double standard over what counts as irregularity in verbs. By the standard we use for Latin, English has a total of one irregular verb. A Latin verb may have a perfective stem that is arbitrarily different from its imperfective stem (compare ferre with tulisse), but this "doesn't count" - we say that it's necessary to memorize four forms of any Latin verb, and with English verbs having only five forms and two of them being always regular, it's a real stretch to find verbs that require you to memorize more than four forms.
† edit: this was wrong; have is also irregular in the present third-person singular.