Players such as OneWeb, SpaceX, and China Aerospace Science and Technology Corporation (CASC) have announced ambitions for their respective constellations with hundreds or thousands of LEO satellites in the not too distant future. The fast motion of LEO satellite contributes to the geometric diversity, allowing for rapid convergence of precise point positioning (PPP), and can augment the performance of the multi-GNSS. In this contribution, to fulfil this purpose, not only the most common polar LEO constellation, but also the heterogeneous constellation which has orbital planes of different inclinations is designed to ensure more visible satellites in low-latitude regions. In terms of the frequency selections of LEO satellite signals, due to the spectrum congestion of current navigation signals in L-band, the S-band or C-band has also been taken into consideration. Finally, the performances of all designed LEO constellations augmented multi-GNSS PPP are investigated based on meticulously simulated code and carrier phase observations. The result shows that the convergence time of GNSS PPP can be dramatically shortened to few minutes or even seconds by introducing a certain amount of LEO satellites.