3 floor house, forced air system - is equal temperature across all floors a pipe dream?

I'm purchasing a new construction house that is 3 floors tall, and one thing I find odd about it is they are using a single 3 forced hot air system to heat the entire house. There are no electronic zoning controls. The system is currently electric restive heat, but I would like to add either AC and either switch to a heat pump or gas for heating. The current furnace is installed on the third floor.

My gut tells me that's no way that I can have equal temperature across all 3 floors with no zones, but I'm looking for input on that, and the best way to proceed.

I see a few options:

1. Rip whole thing out and install mini-splits
2. Separate the ducts into 2-3 systems, and install additional air handlers
3. Install mini-splits on the first and possibly second floors. Use the existing air handler for the top floor only (disconnect ducts to other floors)
4. Install a single multi-speed air handler, and use electronic zoning flaps

Essentially, my questions are:

1. Is there any reasonable chance the current system can provide equal heating temperature? AC temperature (once AC is added)?
2. Do newly installed ducts/systems typically come with any sort of warranty on their suitability - eg if I find my ground floor is regularly 65 degrees while the upstairs is 75, do I have any recourse?
3. What option would you pick if it were your house?

I'd rather not wait until the next heating cycle to find out, as we're just starting to get into the AC season where I am, and I'm hoping to have the AC installed ASAP to use this summer. Thanks!

submitted by /u/LostInTheMaze
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