Quite right. The 20 year rule would effectively be a licence to print money for the founder clubs. They would have a guaranteed income with which to invest and thereby ensure they would be able to mount a formidable challenge within their domestic leagues every season.The point is though, as a founder of the Euro Premier league, United couldn't be relegated....not for the first 20 years anyway. Other 'guest' teams would be relegated but by the time the 20 year period was done the founding clubs would be so rich and entrenched that they would likely never go down, ensuring that they, at least, have the finances to always remain at the pinnacle of their domestic league.
The rest of the clubs would be playing for sixth spot.