Shemuel and the Portable Bathroom

בכורות דף מד ע"ב 

שמואל איצטריך ליה בשבתא דרגלא נגדו ליה גלימא אתא לקמיה דאבוה א"ל אתן לך ד' מאה זוזי וזיל אהדר עובדא את דאפשר לך דלא אפשר ליה ליסתכן מר בר רב אשי איצטריך אגודא גמלא אשתין אמרו ליה חמתך קאתיא אמר להו באודנה

Bechorot 44b 

Shemuel needed to use the bathroom, so his talmidim spread out their jackets and created a divider to provide privacy for him. 

When his father heard about the incident, he said: "I would give you four hundred zuz to go take back what you've done! Announce in public that it is forbidden to wait until you have privacy before urinating. You see, for you it's easy. You have talmidim at your beck and call who will provide you with a divider whenever you need. But what about those who don't have access to that kind of luxury? They will hold it in until they can find a private spot, and it will cause damage to their urogenital tract!"  

Today, a certain talmid chacham approached A"A with a question regarding carrying a cell phone on Shabbat in a case of pikuach nefesh. A"A permitted it. The talmid chacham recommended a gimmick to avoid some of the issur- if the carrier places the cell phone in a bag with something that is not muktze, perhaps he can establish the bag as a basis ledavar hammutar and permit the muktze of the phone! A"A forbade him from making this recommendation. 

"If you add conditions to make it 'extra permissible'," He told the inquirer, "people may mistakenly believe that it is only muttar under these conditions. This might lead them to abandon the actual halacha when your gimmick is unavailable or not being used. And that in turn may lead to pikuach nefesh." 

He proved his stance from this gemara- it is forbidden to add chumrot in such a situation, lest someone else misunderstand, mistakenly believe that the chumra is a necessity, and fail to keep the din properly.