In order to use the leuco form it will need to be contained within capsules which then bind the chemicals to the clothing. Without these binding molecules the dyes would simply fall off or be washed away.
The biggest issue when using these dyes is the problem of washing the garments. Washing the garment at high temperatures may distort or even destroy the leuco molecules to the point no visible change in colour would be visible. Labels will need to be made to highlight what extent these t-shirts may be heated when washed as some of the dyes have different activation levels.
One problem is that the dyes themselves only change colour for short periods of time. This may be a turn off for customers who prefer prolonged changes in colour, however there is a range of colours that offer different temperature levels.