2028 might be a good date to finish, if started timely, the Cetiya at the top, as it might be that Queen Soma was born 40 years before the birth of the Kingdom.
A hundred year after last Sanghayana might be to long, so good within the next ten years at least, and maybe possible, if objecting, such at the foot around the Dhammayut monasteries area the dwellings and gathering within the natural womb nord-west the peak (called after the anicent name of Shiva: Wind ខ្យល់ (in Pakrit, Rudra)). 10 years from now might be a timespan to prepare the undertaking and pre-gatherings of the last Noble Ones.
Just thought, and good to initiate all before soon times changes and stability will require much more effort then in old times.
May the great King and the great leader find soon attention toward an undertaking securing peace for many for most possible times before terrible fast decays globally, now at times where such merits aren't at all out of range.