Mike, I've had another look at the thread and it seems to me that the original post focused primarily on the main advantages of growing ground cover plants emmersed which were as follows:

No CO2
No dosing
No worry about fish uprooting it
No algae
No water changes pulling it up before it roots well.
Creates a thick mat that's very well rooted
The transition to submersed is much less problematic
High biomass
Bacteria is formed in the soil

It was mentioned that this would take about 2-3 weeks but later clarified that the time period would vary with the temperature.

The advantages listed above trumps the issue of speed as far as I can see.

If you're going to abandon this approach then half filling the tank is the same as filling it completely so there is no point in developing a strategy for half filling. You'll not outwit algae by half filling. You may or may not get melting of the crypts but so what? That's what crypts do and they grow back if the nutrients and CO2 are added properly.

Once the plants are submerged you'll have to start dosing, and adding CO2 like any other tank regardless of the water level.

Cheers,