When I open up the 12" deep hive I counted at least 12 to 16 queen cells with only 3 or 4 yet to be capped. ...
The queen cells are on two to three frames, all foundationless fully drawn.
Finally to the question. I am thinking of splitting this colony into two.
It seems that you hive is going to swarm. The most important is stop it.
Do they have room enough or why they are going to swarm?
There is no reason to take those queen cells and wait that they are going to lay eggs. During this time you get egg laying queen and you get one generation new bees.
1) Now order at least one new queen or two.
2) Move your hive 10 feets
* put new deep on old site.
* there brood frame and the queen and the rest foundations
* that will stop swarming.
3) When queen cells are capped, give to "new place hive" the new queen.
4) Your recent queen is swarming type and it is better to change.
If you want to get honey, you should put together hives when foundations are build. If I were you, I should not split the hive during honey season
What I should do :
I should do 1-3 operations.
* After a week when foundations are drawn upp I should join the hives for honey.
* from another queen I should make a 3 frame nuc which starts a new hive.
If you dewide the hive, you will not get honey any more.
When honey season is over, you can strengten the weaker hive with brood frames and you get a normal hive for next year.