Oh I believe in theory a 50Mhz CPU is capable of doing almost everything I need, but it just lacks the software optimized for it. I think a week to compile everything is too optimistic.
I did valuable work on a 2 MHz Apple II with a 4 MHz Z80 add-on running CP/M that I used to write the documentation. The documentation part was just as fast forty years ago as it is now but assembling the code was glacially slow. The 6502 macro assembler running on the Apple too forty minutes to assemble code that filled an 8 k EPROM.
6502 assemblers are amazingly fast on more recent hardware. Something like 60-70ms to run a script to assemble and link an a version of msbasic (AppleSoft) on my old laptop.
And even if the CPU is 50 MHz, modern DRAM and NVMe flash are very fast compared to memory and storage on 1990s (or older) machines.
Older versions of Microsoft Office (etc.) ran about the same on 50 MHz systems as Office 365 runs today.