Thought about combining each of a 5GHz CPE like SXT lite 5 and a 2.4GHz Router devices and connecting them via ethernet for consumer like we all are probably using. But that looks a bit hassled and costly solution. And cost is important to us for the case of consumer. So I've been seeking a dual band device and I don't know it's possible or not.
What it will do is; connect to the central APs with help of an external Antenna and then serve the consumer devices wirelessly or whaterver else.
is there any option in Mikrotik device?

Your picture is wrong. Paint the walls much thicker and some trees around the house and you see the problem of your idea. If you use an external Antenna you have to use 2 thick coax cables to do mimo. If they are longer or thinner you loose signal.
Technical much better is one device/AP inside which is connected with an ethernet cable to the CPE outside. With 5 GHz you want to avoid signal travelling through coax cable.

Your picture is wrong. Paint the walls much thicker and some trees around the house and you see the problem of your idea. If you use an external Antenna you have to use 2 thick coax cables to do mimo. If they are longer or thinner you loose signal.
Technical much better is one device/AP inside which is connected with an ethernet cable to the CPE outside. With 5 GHz you want to avoid signal travelling through coax cable.

I just want to know is it possible or not? Usually within 1 KM radius we can use like this device in top floor

A dual band router + external antenna will cost more and perform worse than a SXT+router.

Your picture is wrong. Paint the walls much thicker and some trees around the house and you see the problem of your idea. If you use an external Antenna you have to use 2 thick coax cables to do mimo. If they are longer or thinner you loose signal.
Technical much better is one device/AP inside which is connected with an ethernet cable to the CPE outside. With 5 GHz you want to avoid signal travelling through coax cable.

I just want to know is it possible or not? Usually within 1 KM radius we can use like this device in top floor

You should visit another wisp to see what works and what does not. Looking at your other posts you need a trial/learning phase to get a feeling for wireless or you will fail. You have to learn that you dont want to connect customers through walls. This does not save your money it will make you angry customers.
You need some knowledge you don't get by asking some questions in a forum. Sorry if this sounds rude but it will save you money.