I don't see how it would be, unless by "subtracting individual mandate" you mean "replacing an individual mandate backed with a fee/tax/penalty for failure to comply with a universal tax, an option to select a private option with the tax refunded as a subsidy, and a default of using the public option if no private option is selected". Which, really, is retaining the individual mandate, but making it impossible to break rather than penalizing breaking it.