DFC, there will be more fuel burnt because it takes more miles to lose that extra 1000' and if number 1 needs an extra 3 miles then the all the following aircraft will be 3 miles further back (that's a lot of wasted fuel for a sequence of 50)
If approach can't get the correct aircraft off the stack because there are not enough levels available then
1) the most expeditious landing sequence cannot be followed (more delays for everyone following)
2) Aircraft may 'lose their place'. unfair on the ones at LAM (or holding out at Braso)
3)There may be gaps on the approach if all the aircraft are through one stack. One level at LAM in particular can often be blocked by survey flights, that just leaves 2 levels to vector off the hold to maintain a landing rate of 40+, that's just not possible.
On paper it seems like a great idea but the landing rate will suffer, maybe not a problem when it's quiet but once traffic levels increase a lot of questions will be asked about why the landing rate is so low.