Consequently, it’s a terrible idea.
If anything bigger buisnesses have more ressources to avoid taxes. - Thus having everyone pay the same would lead to large companies paying more than they do now and small companies would be barely affected.
You will have to go after financialization tricks, where healthy companies get loaded with debt, weird tricks with assets and all the stuff the finance industry comes up with that has nothing to do with core function of the company. Now imagine the powerful lobby you have to work against.
Food for thought: in a distribution chain you will find lots of small value adds. Take sea ports, there are loads of companies that handle import of materials or products. The price they charge for their goods/services are dominated by their import costs.