As much as it makes me sound full of myself when I state this, honestly, I'm going to save myself (and yourself, to a sense) the trouble and just say,
take a look here quick.
Off the top of my head, if there's some things you'll question, there's,
Why not use Smilodon Mantle +1 on Y/G/K, or at least Gekko?
I feel as if the attack will guarantee me that extra nudge on some things in particular, on top of, in my
own opinion, that the ATK boost doesn't apply to the second hit on a Y/G/K, when a double attack occurs.
Why use only one TP build?
In my own opinion, it isn't worth the hassle even in the slightest to make diverse TP sets, when generally, as an example, the extra damage you'll gain from [briefly] swapping Cuch. Mantle to a Cerb. Mantle +1 would literally be a double digit increase to your damage in-full, triple digit at best, but even then, your total damage by the end of whatever you're doing would already be +50k at least. 50,234: oh my.
And, your own ideal question I believe you were asking (as I skimmed through the thread slightly),
Why use pure attack/accuracy over modifiers for Penta Thrust?
Oddly enough might I add, I do use Rana in the same fashion (as well as all the Ninja weapon skills on an additional note), simply for the fact that once a modifier on a weapon skill (especially multi-hit) reaches 40% or below, it honestly becomes hard to notice improvement-wise.
I used Myochin Kote +1 and Cuchulain's Mantle full time for a while on Penta Thrust, but then a
friend of mine in the Salvage static we ran with, who was "lacking" M.Kote +1 at the time, was using Bandomusha Kote instead to suffice until he got the Limbus pieces for his kote... was commonly beating my Penta Thrusts in Salvage, with that one gear piece difference alone.
I brought out my Bandomusha Kote from storage, and I instantly noticed the difference the following Salvage; I haven't looked back ever since, and my 'kote +1 have been collecting dust instead. With such discovery though, I've also gone as far as to make two different Penta Thrust sets, specifically each being either accuracy, or attack; neither modifier-related.
Vegetto has like five(?) Asuran Fists macros, so by no means am I gloating when I say I have two different Penta Thrust sets, but they really are needed at times, even though I honestly rarely ever use my #1 (accuracy), since whenever I'm using polearm, I'm either [nearly] capping accuracy on easier, squisher stuff with 8/8 merits in my #2 set, or I'm eating marinara pizza +1 and that's capping my accuracy in my #2 set as well.
I'm sure dudeface'll show up in the morning here regardless, but just chiming in until then; hope it helps. :|