Hi Hive account@xorimaxo, I'm no expert (!)... but from what I understand there's no need to be worried about disproportionate taxation: rather the normal taxation on profit on investments & speculation. Rough said: up to ca max 50% for pro traders, 30% for speculation (most common I guess, and possibly considered default) and zero for investing (you could say: buying and long term holding...like when you bought BTC in 2016 and now you sell some if it). Some interesting articles and discussions (in Dutch):

• articles:
  https://www.smartbiz.be/nieuws/173704/belgische-fiscus-krijgt-33-procent-van-privewinst-op-bitcoin/
  https://m.tijd.be/netto/belastingen/Moet-u-belastingen-betalen-als-u-in-bitcoin-belegt/9958726 1/12/17
  http://bitcoinbelgie.be/bitcoin-en-belasting/
  http://m.newsmonkey.be/article/86426
• fora:
  https://juridischforum.be/viewtopic.php?t=84687
  https://juridischforum.be/viewtopic.php?f=16&t=74039