The main thing necessary is that it never sends anything to the PICAXE until the PICAXE has indicated it wants it, and is then ready for it, coupled with a mechanism to let the PICAXE know there is something there which can be asked for - this is assuming a normal non-X1 PICAXE without HSERIN.
Importantly though when trying to get a company to do something, a convincing case has got to made for that, either a business / economic case, or a direct appeal to their engineering side that it's a worthwhile or useful thing to be done.
That means having to be able to very formally define for them what the issues are, what the problem is, how it could be solved, what solutions would not work or not be acceptable, and why it is necessary or desirable for them to do this, along with the benefits gained.
If you don't want your effort shown the door, it helps to build up a rapport and relationship with the company themselves and to be very knowledgeable about the product and how it works before 'dictating' to them.
Business influence is a strong force - "If you add this I'll buy a million pieces, or go somewhere else" - but individuals can have a much tougher time of it and have to be more creative in their approach.
Once you have your PICAXE-SimpleLan UDP passing system working you'll be able to identify what the weak points are and how it could be better or more PICAXE friendly, and that's when you'll be in a good position to be able to define what needs to be done. You should also be able to determine if a solution proposed is good enough or not, so you can stand your ground and not be 'fobbed off'. But don't be too inflexible; it's all about persuasion, usually of the subtle variety - You're helping them make their product better, not criticising what it lacks, inviting them to add things not demanding.
A good course is to convince someone that your good idea is their good idea
And remember, "wouldn't it be nice if a PICAXE ..." is often far more productive than, "If you don't add this, I'm off elsewhere".
Of course, you could just say, "add this", and you may get lucky, but you don't want the door shut permanently after the first approach.