My dear friend
When you have not attached /enclosed any format of offer letter; UPON WHAT do you expect the members to give their feedback ???
That is exactly what I meant; instead of asking members for a ready-made "impressive" offer letter,
(STEP 1 ) - you should first DRAFT an offer letter on your own, highlighting any special feature that you would like to be there to make it more "impressive"
(STEP 2 ) - you can then attach the offer letter format with your post, and seek suggestions.
(STEP 3) - the interested members can then vet you draft, offer suggestion / modification / replacement etc. as per their opinion based on their experience and expertise.
(Kindly Note) - in any organization/institution, this is the way to ask for help from seniors and peers. One does not ask point blank to someone to produce something as per your wish (unless that person is your sub-ordinate and is paid to help/assist you).
Hope I have made myself clear.
If not; I"ll paraphrase it, once again for you;
"KINDLY SUBMIT A DRAFT OFFER LETTER MADE BY YOU; THE FORUM MEMBERS WOULD THEN BE PLEASED TO HELP YOU OUT."
Regards.