I think everybody hates when you need 10 buckets for a little bit of crafting, it would be cool if you can use a portable tank in a recipe, 8 times

What do you mean by "10 buckets for a little crafting?" What recipes should I use it in?

Exactly

I think he means any recipes that use water/lava/whatever buckets for crafting and give back the bucket after crafting. For example if a recipe needs two buckets of water and I need 10 of that item that means I have to have 20 non-stacking buckets in my inventory and swap them out after every crafting operation.
Portable tank feature would be that it remains in the crafting grid and just gets drained by 1 bucket of its contents for every operation.

Ohh. This is not possible at the moment, but if it ever is I will definitely implement this functionality :)