"Facade" vs. "façade"
Solution 1:
According to Google ngrams, "facade" is far more popular than "façade". So I would just write "facade" unless you want to emphasize the "Frenchness" for stylistic or marketing reasons.
Solution 2:
The cedilla (ç) beneath the letter ‘c’ is used in French to show that it is to be pronounced as /s/ and not as /k/. Most French people will know that anyway, so it is as otiose in French as it certainly is in English. Since facade is now an English word as much as it is a French one, there’s no need to follow French practice.
Solution 3:
The cedilla helps, imo. Just reading the replies above made me think... hmm... "facade"... hmm, is that faKade? a secret move in fencing?
then I looked for examples that would leave us wondering whether the sound should be "ss" or "k". Thought of "percutant", French for "percussive". The plain "c" indicates the need to pronounce correctly: "perKutant". And no need to know the word or be familiar with a word to pronounce it correctly. No faKade, no perSSutant, all is fine.
Note: I put in two "s" in examples because in French, one "s" only inside a word is often if not most of the time pronounced as /z/ : crise (crisis) pronounced with "z" sound. Bise (greeting kiss) same thing. Mise (placing) same again.
sorry for butting in, these are thoughts that occurred to me as I was passing by. This site was useful, I have bookmarked it. :-) A native French-speaker who also loves English.
Solution 4:
Yes, much as people still spell café with an accent. Cafe without the accent just isn´t the same. We all know, French or otherwise, that that last e must be stressed because the accent is there. Otherwise we would just say caff or caif.
Solution 5:
There is no need or purpose for using the French cedilla in the English word FACADE. Yes, the French word is, and has been, English for a long time. So it's just a pretension at this point, and functionally unnecessary since we know how to pronounce the word through usage.