The average PC104 system is a much more powerful computer than an Arduino; usually (these days) near desktop-PC class (32bit cpu with floating point, ~1 gigabyte of memory, standard high speed buses, disk support, etc), and at a price 10x of Arduino as well.
Can Arduino host FTP server or other servers?
Not really. An Arduino does not have any networking built in. Nor files.
What about its electrical (power) consumption, the calculator strength, its range possibilities.
A typical Arduino uses less than 0.5W of power, runs at 16MHz, as a total of less than 40k of memory, and does about 16 million 8-bit additions per second.
Can we plug/unplug it without injuring it (is it solid).
An arduino is probably similar in "solidness" to a PC/104 system.