And the two major alternative starting points used in practice are Roman law or Sharia law, both of which are likely even less acceptable to someone who doesn't want the baggage of English common law.
On the other hand, in the civil law systems when new countries are formed, as soon as you get the core laws passed (which takes some years of transition) you do generally make a clean start where only the new code of laws matter and everything else is discarded - you explicitly choose which parts of earlier code get included in the new laws, and that's it, old laws get pulled out only if there's a relevant dispute about some events which happened back when those old laws were in force.
