Programmer's got cut off from the microcode starting in the 80s, had this not been the case, I think we would have seen more activity lower in the stack.
ISA lockin is a much smaller issue now.
DAISY https://www.microarch.org/micro33/tutorial/tutorial.html
FX!32 http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.23.2...
I've recently been studying AM2900 (bit-slice) processor design. There are still people out there putting microcoded systems together on FPGAs!
I am investigating it, because I think there might be some useful design aspects that could be re-used, but mostly out of retro computing interest :)
https://en.wikipedia.org/wiki/AMD_Am2900#Members_of_the_Am29...
There are two other branches of system design which are really interesting
* CGRAs, Course Grain Reconfigurable Architecture [1]
* FPGA Overlays [2]
[1] https://cgra-me.ece.utoronto.ca/[2] https://ieeexplore.ieee.org/abstract/document/6239797 https://www.seekdl.org/conferences/paper/details/9227 https://www.semanticscholar.org/paper/An-efficient-FPGA-over...
The original Rosetta used the same underlying tech with the exception of the memory model stuff, but Transmeta never had to deal with that since they only handled single cores. (And Sparc shipped TSO/WMO switch from a control register all the way back in the mid 90s).