You can try out the Proposal Review template on Simitless.
you can either use it as is or take it as inspiration and modify it by deleting or adding new columns (or creating new things altogether),
it takes .csv documents, so you can import and export them at any time,
for reviewers to access and make leave reviews, you (if you are the one creating the app)...
I would suggest the following strategy:
using a little python script to convert each line of the .csv file(s) to separate markdown or ReStructuredText files ensuring that each proposal ends up with the same filename each time.
Setup a Private GitHub or similar project for the members of the conference.
For each file - i.e. proposal, raise a PR to add it to ...