That's an interesting way of looking at things. Kudos for the creative thinking. Typically we pit
pot odds against the odds of hitting our outs.
From the outset, it seems like a great
bankroll management strategy. You are limiting your downside to 5% of your bankroll and when you win you will win at least 25%; great risk/reward ratio.
However, how often do these opportunities come along? And when they do come along, what kind of circumstance do you find yourself in?
Let's assume that this is the only strategy you employ in your play (i.e. the rule is the only rule you use to determine whether or not you enter a pot.) Then (assuming no antes) you will only be involved in a pot if there are many other people in the pot before you (to get 5 to 1 pot odds preflop would mean that at least 3 people other than SB and BB would have to be in the pot already in order for you to consider calling). So this means you never call from the first 3 positions and you only call from the 4th position when every single player in the first 3 positions is involved in the pot having bet the same amount (if one has a different bet amount, then that changes the x to 1 pot odds from x=5 to x<5).
So now you find yourself in a situation where when you are involved in a pot, you are always involved with 4 other players and 3 of those other players more likely than not have you beat because they voluntarily put money in the pot based on their hand values (and since they are in earlier position than you are, they would theoretically need stronger hands than yours to call with from those earlier positions). So not only are you in with 4 other players, but now it is likely that at least 3 of them have hands that beat yours.
Now you didn't say this is the only rule you use throughout a tournament or cash game. I don't see how the rule helps you achieve positive results regardless! I think any kind of rule that you come up with involving pot odds needs to be connected to your hand value.