Trump’s plan is the status quo, leaving the giant IRS bureaucracy and making it a costly nightmare to comply with. Trump retains the progressive rates which are nothing but a socialist, class warfare tool.
Everybody is going to leave the IRS in place including Cruz because there is no will in the US Congress to get rid of it. Its easy to be against something that you know will not change. If Cruz really thought he could get rid of the IRS he would just go for a sales tax and be done with it.
Trump has accepted it and is lowering tax rates on individuals and on business. He is not trying to sneak a VAT in on small business.