You could do what you’re proposing.  Its called “arranging”.  No big whoop.  Keep in mind that any notated sound, weather it be the standard fly-speck of music or the loops and swirls of a persons signature, is only a visual reference for an aural result.  You first have to know and understand what the player or reader is going to interpret by seeing your part.  Take for instance a tune written as a reel versus the same tune written as a hornpipe.  Both will be in 4/4 or Common time, but the beaming of most reels seems to be two sets four 8th notes per beam while the hornpipes will be four sets of two 8th notes.  What’s the difference?  Where you feel the pulse of the music (two vs. four pulses per bar).  Also in hornpipes the first bar or two is usually notated with dotted 8th-16th rhythms to indicate the “swung” lilt of the melodic line.  They only do the first few notes of a piece for a couple of reasons.  First, it saves time in notating the work.  Second, it is much easier to read and when dealing with such an abstract (like a dot on a page representing a musical thought or emotion) less is more.  The responsibility is on the player for inserting all the extra nuances that will make a line music rather than just pitch in time.
As for your quandary of 6/8 vs. 4/4 with triplets, be aware of the major, minor and secondary beats.  The down beat should be considered the most important rhythmic anchor of each bar.  How you split up the bars will impact the piece."
6/8 feel like
1,2,3 4,5,6 |  1,2,3 4,5,6
4/4 with triplets Feels like
1,2,3 4,5,6 7,8,9 10,11,12 |  1,2,3 4,5,6 7,8,9 10,11,12
Synchronization-wise they will both time out to be the same.  Emphasis/feeling-wise, they’re different.
As far as hyper notating a melody to be an absolutely perfect representation of a melodic line, it’s about like overdoing English for the same result.  Take for example, the name “JOHN”  If you wanted to, you could annotate this by writing down exactly what your mouth does…
DZZHHHAAAAAAAAAHHHHNN.  It’s more accurate maybe but it doesn’t help the performance.
Best of Luck! 
Scott McCallister