My wife helps organize a vegetarian community kitchen. She recently had a request for tiramisu-like dessert but there are a number of restrictions:

• The time frame of the kitchen means they only have two hours to prepare it before eating (including chilling)
• They cannot use raw eggs
• No alcohol
• No cheese (the woman requesting doesn't eat cheese) but other dairy is okay

My wife would like to try to accommodate the request if possible.

She was thinking replace the traditional mascarpone custard with a mixture of Greek yoghurt and whipped cream (do you think the whipped cream needs to be stabilized with agar agar?).

Does this sound workable (she has never tried this before and is not a professional chef)? If not, is there a better plan, or does this request sound like an impossibility?