Are irregular plots or structures recommended ?

No, The classical works are very clear in stating that the structure should be a perfect square or Rectangle.

1. According to Brihat Sanhita irregular shapes gives following results :
2. When South East is cut, the owner will lose wealth and will be miserable through women.
3. When the North West is cut there is loss of money and food.
4. When North -East is cut he will fall from virtues.
5. When the South-West is cut there is death of male children, troubles through women and the master becomes servile.
6. On the other hand if all the angles are right the inmates of the house will be happy and live with wealth and honor.