His disciples do not "need" to see Him to believe because they walk by faith. But how much more would a disciple's faith strengthen when they do:
1Pe 1:7-8 These trials will show that your faith is genuine. It is being tested as fire tests and purifies goldthough your faith is far more precious than mere gold. So when your faith remains strong through many trials, it will bring you much praise and glory and honor on the day when Jesus Christ is revealed to the whole world. 8 You love Him even though you have never seen Him. Though you do not see Him now, you trust Him; and you rejoice with a glorious, inexpressible joy.
The term revealed is defined as: appearing, coming, lighten, manifestation, be revealed, revelation. Would the "whole world" not include His disciples? Furthermore, notice it states they [His disciples] do not see Him "now". The literal translation is "at present". The Greek adverb for "now" [arti](at present) connotes the idea of suspension. In other words, they do not see Him now, but will later!
1Ti 6:14-15 that you keep this commandment without spot, blameless until our Lord Jesus Christ's appearing,15 which He [The Father] will manifest in His own time, He who is the blessed and only Potentate, the King of kings and Lord of lords, 16 who alone has immortality, dwelling in unapproachable light, whom no man has seen or can see, to whom be honor and everlasting power. Amen.
Verse 15 is actually referring to God the Father who alone has immortality. It cannot be referring to Christ because He has been seen. Additionally, the verb "has" is in the present tense. By this time, Christ had already ascended to the Father as an eternal, immortal spirit being. Paul could not be implying Christ is the "only" one with immortality. Although Christ is the subject of the last clause in verse 14, there is a transition made at the beginning of verse 15 that switches the context to the Father. Some argue against this transition but a look at the word order in The Greek-English New Testament dispels this argument:
Notice how the numbered word order indicates the phrase "shall show" should be the last phrase (#6) of verse 15. When the Greek is translated correctly then the transition from Christ to The Father becomes apparent:
"...the appearing of our Lord Jesus Christ; Which in his own times the Blessed and only Potentate shall show" (1 Tim 6:14-15)
The Blessed and only Potentate is the one who "shall show" or set the time of Christ's appearing!