Are you just trying to express a conditional situation without si, or are you specifically looking for some kind of subjunctive conditional (with inverted word order)? I know very little French, but for the former, you might be able to use quand. As for the latter, I don’t think you’re going to find it.
Note that English does something similar, using should:*Should he arrive home late, he’ll get an earful.*I think this is something particular to Germanic languages, so I don’t think you’ll find it in French, but I could be totally wrong.
I think you could make the first part a question to avoid the “si/if/falls”.
Example:
FR: Il rentre tard? Il aura des problèmes!
EN: He will be home late? He’ll be in trouble!
I think you could also you “en cas”: “En cas de retour tardif, il aura des problèmes.”
But that might be me trying to press German sentence constructions into French.
The ‘should’ is equivalent to ‘if’ in that case, but in dialogue you’ll find it used without any conditional in front, “He arrives home late, he’ll get an earful”. Inflection helps clarify the meaning, and when I hear such things they sound like they’re being said with a German accent just as my grandmother would have used the form.