we would love see eevblog calculator.
I just think the practical way to do this is to make a phone/tablet app. It is really hard to make a quality calculator with labelling that does not wear off and buttons that keep working reliably. It needs to have very long battery life (or solar power). Otherwise you have one more device that needs to be regularly charged and I have too many of those now.
The HP CAS (Computer Algebra System) used in the HP 49G/50G is open source so perhaps that can be used somehow. Using a touch screen phone/tablet, you get the possibility of interactive graphing. You get a fast processor.
Using a phone also gives the possibility of connectivity. Back in the late 70's/early 80's, I used to use the HP 9825A desktop calculator that was a computer/calculator that also had the option of GPIB/Serial/Parallel connectivity. So you could capture readings from a HP voltmeter into an array, and then use the calculator or embedded HP basic to crunch the numbers. I just loved using the 9825A.
Otherwise, if I need electronic calculations embedded in an ordinary calculator, I just program one of my HP calculators with the wanted functions. My HP49G labels the F1-F6 function buttons with the commands I have programmed, so works great.