I would if a) you have complete faith in the seller, and 2) the tirette is in a skin that could be replaced at Hermes. If the bag is totally rare, I'd overlook the missing tirette though. I usually have mine on my bags so it's something that I would want, but I'd forgo it if it were a bag I knew was rare and/or at a great price.
I trust the seller, I have bought a couple of things from them.
Condition is that its nearly perfect with no cracking, or leaching of leather, I guess when I buy my next H bag I'll have to remember to get GH to match.
DH has suggested I get a masterlock for it, he thinks it might look avante garde.
My reaction was :
I would if I know it is a bag I am definitely keeping for life (ie. for me it would be a black box 28cm kelly with gold hardware, as opposed to a colored one I may change my mind about) since I don't use my kellys with the keys, lock and clochette anyway.
Heck yeah! If it were a grail Kelly in otherwise excellent condition and the price was fair for a bag without parts.....then I wouldn't hesitate. Especially if you have already worked with the seller successfully......I'd just do as DQ suggests and dangle a great cadena off her hardware!!!!