Not bad but the only problems is Summoning is how IS makes their money so a larger pool = worser odds for player which means more money for IS.
I don’t think we will see a split pool honestly we will get a lot of demotes in April though like a lot of gen 1 units that shouldn’t be 5 star so look forward to that.
Yes more units are being added but they are a lot better than gen 1 units with better skills/Stats and generation bst increase
I know of a solution to the summoning saturation problem.
Take the units available on normal banners, and separate them into two sets, and have one set of units be available in the normal summoning pool, and int eh middle of the month change to the second set of units.
A system like this would pollute the summoning pool a lot less and give people a more methodical way of spending their orbs, for example, if you wanted a specific 3-4 star unit, you could save your orbs until the time of the month where that unit is summonable.
Banners would ONLY make their focused units have a chance of appearing during summoning, this way if one banner with new units ends while another banner is up that you also want units on, you could still get the new units despite both banners having been up at the same time before.
Answers
"We will get a lot of demotes in April though like a lot of gen 1 units that shouldn’t be 5 star so look forward to that"
Way to set yourself and others up for disappointment. We don't know if demotions will happen, and if they do, we don't know if they will include 5* exclusive units or not.
Also "a larger pool = worser odds for player" is not true. The size of the pool doesn't matter, it's the color distribution of the units (unless you are aiming at a 4* unit or a 5* off-focus unit). The chances of getting a 5* focus are the same if the pool is 50/30/20/15 red/blue/green/colorless units or if it's 10/6/4/3 units.
A separation of the pool would be a better solution to me than 5* exclusive demotions, as it has a chance to actually make an impact on the summoning experience (no more red hell for instance), while the other is just repeating the same old misstakes that brought us here. We'll see what happens in April.