Curates-egg, if the 20,000 "regular" verbs were as common as the 250 "irregular" verbs, everything you are saying would make sense. However, the 250 "irregular" verbs are in fact among the most common verbs in our language. In that sense, they are the rule, not the exception.
I think I've said everything I can reasonably on this matter. Thanks for your patience. :)
I suspect that a thorough linguistic analysis wouldn't lead us to the conclusion that the strong verbs are regular. Different patterns have been mixing for thousands of years which results in a bit of a mess. The evidence for this is that some verbs have several irregular (that is not ending with "-ed") forms.