That will probably work pretty well. A lot of the poor reputation of AC’97 comes from the very poor quality analogue components that are typically used in the analogue end of on-board sound cards. Also the high gain required for microphone pre-amplification is much more demanding than dealing with line-level.
With a reasonable mic pre-amp I’d guess that the difference will be subtle. Getting the 50dB or so of gain to boost the mic level signal up to line level without introducing noise and distortion is the hardest part.
If you want another project to hang around for several years, you may be interested in this snippet that I stumbled upon recently: SSM2019 monolithic pre-amp chip