[hteas]

Jonta,
Your idea sounds as good as any. Practice it for at least a few weeks, and then try a max hold to see if you've improved. There a lot of freedivers, and no single technique will work for everyone. If you don't improve, try something else ; )
Exploring what works best for you is the best thing you can do.
I either do pairs; breathe one, hold one, breathe 2, hold 2... and up to my max of 4 min, then back down
or I do a series of empty lung negatives, with one minute between holds, with a rather painful max once in a while of 120 seconds. Thats what seems to work best for me.
Howard