Sensitivity: The minimum requirement for WFTP is that FPs mimicking a Jupiter-like planet of a solar-like star of mV=12 mag can be excluded. This requires that the lightcurves of eclipsing binaries with mV=17 mag can be measured. In order to exclude FPs that mimic Super-Earth-like planets, we typically need to exclude stars down to mV=21 mag. This is easily possible with the OSN and the typical weather conditions there.
Field of View: For precise relative photometry we need a number of comparison stars close to ecliptic poles. For small field-of-views quite often the comparison stars would be much fainter than the targets. Then the photometric accuracy that can be achieved is limited by the S/N of the comparison stars, not by that of the target. WFTP offers a field of view of 29 x 29 arcmin.
Wavelength Selection: The filters have to combine suitable bandpasses with a high transmission. Available imagers use standard filters that are not ideal for the TESS follow-up observations. WFTP will provide two filters. While the red one resembles the TESS spectral response function, the blue filter supplements the TESS results with color information.
Weight: Available instruments can not be used with small telescopes, although it is impossible to obtain on larger telescopes the large amount of observing time required for exoplanet programs. A modern instrument has to be lightweight. WFTP weights less than 20kg.