"Enableable" is possible, but it's not a common word and it's a little difficult to pronounce.
If essential to the idea is that something is not presently enabled but can be enabled, I think I would use a phrase, like "can be enabled". Depending on the context, you might simply use a totally different word, like say the thing is "available".
Afterthought
People on here often ask, "What is one word that means ..." Often the correct answer is, "There is no one word that conveys that meaning. You have to use more than one word." While of course it's convenient if there is one short, simple word that expresses an idea, I'd say, Don't be afraid to use multiple words. A single word is not always better. Sometimes there is a single word, but the word is rarely used so most of your readers won't know it and will have to guess what it means. (In theory they could look it up in a dictionary, but for most that would be way too much effort.) Or it could be difficult to pronounce or awkward for some other reason.
The only reason I can see to insist on a single word is if you are using it over and over again in a document. If you're going to say it once or twice, using several words should be no problem. If you're going to say it a hundred times and it takes ten words to express the idea, then yes, this can get verbose and repetitive. In that case, I'd say okay, use an obscure word, or invent a word, or attach a specific meaning to a word that ALMOST means what you want. Then explain it once and use it many times. Like, "In this users guide, when we say that a feature is 'available', we mean that it can be enabled from the User Options menu ..."
Selecting the students indiscriminately makes fairness questionable.
Selecting the students indiscriminately makes the fairness of it (all) questionable.
is correct meaning the selection process has flaws and questions.
If we choose the students indiscriminately, then fairness becomes a question.
if we choose the students indiscriminately, fairness may becomes a question.
If we choose the students indiscriminately, fairness may become questionable.
might be a better phrasing for the hypothetical outcome.
The strange part about your statement is that choosing students indiscriminately (without discrimination) is the same as at random which can be deemed as fair. The problem is usually when there is some type of discrimination involved.
If we are not careful with our selection metrics, they may be questioned for discrimination.
To go under question is more a legal term for questioning a suspected criminal
he was put under question at the police station
and would not really apply to something inanimate like a selection process.
Best Answer
How about... Your language helps write robust and fault-tolerant software.