What's the nightmare there? You need a single simple report (excel sheet?) from the mining pool and just total them up.
Hundreds or thousands of events is nothing special - if your income would come from selling stuff in a tiny shop, you'd likely have that many receipts to report.
Many people have mined across dozens of different pools over the years (and for different currencies as well), and many of those pools are now defunct.
I believe you just stated the new killer feature for mining pools. Miners will presumably dump pools which make their taxes harder for pools which make them easier.
Hundreds or thousands of events is nothing special - if your income would come from selling stuff in a tiny shop, you'd likely have that many receipts to report.