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it is designed to be serviced from the opening provided for adapter plate. No need to disturb the tiles . It may be a new thing in india, however concealed cisterns is decades old and most of the reputed companies have proven designs. However...
The design need to be adapted to local \indian water conditions, The amount of debris \ silt is something that can cause interruption in valve closing , typically tanks with rectangular design has higher chance of clogging. you need to choose something that is sort of 'V' shaped at bottom. the sloped bottom doesn't accumulate ,rather funnels silt \ debris out. some other designs have filters at inlet , that may require cleaning.

Kohler is one such company that I know which has customized the design. its economical 3.5k to 4k for tank and 1.5 k for actuator plate.
Care needs to be taken while plastering and tile laying , GI Mesh barrier, such that the plastic tank does not get compressed (depth dimension) due to stresses of cured plaster, disrupting the internal mechanism. Thickness of plastering \ tiles ,finishing need to be proper so that Adapter plate can be easily fixed.The company technician will give a free visit for instructions of installation. Do not depend on the unskilled labor for installation.

@ Nivas,

Thanks a lot for the insight.

Regards

Good discussion.
After some thought, i have decided to get away with flush tanks for my newly constructing house (G+duplex)
Going for direct flush using 40mm flush valve. This will be supported by dedicated 1.5" pipe line from overhead tank.
Anybody tried this? will this work effectively?
Any method to make it easy for future maintenance of concealed flush valve ?
I have seen flush valve going for toss frequently in my office.. so, sure we have to be prepared for repairs...

Well. I found some good articles online explaining why avoiding flush tank may be a good idea.
Based on following points, i moved away from flush/concealed tanks - used 40mm pipe (1.25" pipe also will do) pipe line from overhead tank to each bathroom and then use reducer for internal connections.

Advantages of using flush valve:
---------------
Wall thickness -> Concealed tanks required minimum 8" wall.
Water consumption -> Flush valve is more controlled in terms of water consumption. Variable quantity of water can be let out depending on how gently we push the valve.
Refill time -> In tank system, after flushing once, it takes considerable time to refill. whereas, in direct flush you can flush n number of times.
Less Cost -> Additional cost on tank and labor. Requires expert plumber work.
Space savvy-> Flush valve is simple. Can be installed on 4" wall and ledge wall also may be avoided.
Better pressure -> Flush valve connected to tank provides better pressure for flushing
Better to reuse -> One more basic thought is : Since we have overhead tank acting as storage at higher pressure, why to additional storage units in every bathroom??
Last but not the least: Tanks because of mechanical action are prone for repair. Any maintenance will be difficult with concealed tank - may require break-opening of wall/tiles/ masonary etc.

I agree with navhe, maintenance of the concealed tanks is too much. i have these at myhome and it works well but sometimes when it starts leaking all the water in the overhead tank gets wasted. bad part is if there is a automatic controller then water from sump also get wasted.
i feel for all maintenance reasons direct flush is good.
In one of our houses which we have rented out we have direct flush system and no issues for the last 2 years.