Here's my $1.00CDN worth
1.) As far as tech sharing goes, I think we have a good system for that now (1 a month, 'gold' techs only to minors, China, France, Italy, no docs ever), as long as it can't be easily circumvented.
2.) Not sure how that is a problem, but I may be missing something. Unless you are speaking of expeditionary forces. IMO, the only problem with them is using them to invade (usually) the aggressor nation. In the case of amphib invasions, our house rule against neutrals supplying beachheads of nations at war will make that a silly idea.
I have 2 ideas for that. One is simply a 'hands-off' rule for exp. forces. You lend the forces, the only control you have over them is to take them back. Alternatively, a rule could be made that all exp. forces supplied by neutrals must remain inside the prewar borders of the receiving country. ( I think we all know where those are.) In the case of exp to allies, not allowed. (military control will give the same freedom of action, without allowing supply exploiting. This IMO actually would eliminate the need for the 'Greek statute { don't want to name names

})
3.) I don't think there should be a restriction on who could ally with who, although possibly a time restriction on alliance switching to prevent exploiting
(eg. If you leave an alliance, you must wait one year to join another)
4.) I don't think this is a problem, since I've noticed in most games the sides are pretty even (based on historical alliances)
If each country plays in such a way as to be as self-sufficient as possible, IMO this will address a lot of issues. Again, I may not be understanding the point here.
5.) I would prefer not to have USA singled out by special rules, and I think the problems with USA can be minimized with the right 'blanket rules' that apply to everyone.
One idea I have is that neutrals cannot ship supplies to other neutrals. This would reduce massive USA supply infusions, and IMO makes sense.( All countries start with a sufficient peacetime economy, so why would they need extra supplies?)
This would still enable Lend-Lease and supplies to China, but only when they were at war and might possibly have a need for it.
I realise that implementing any or all of these suggestions might have unforeseen effects on either of 3 sides, but we will just have to try different things until we get the game we want (although IMO, the host should have final say and we should play the game he/she wants (No offense DieFledermas, just being generic

) If we do not like the game style of the host, we are always free to start our own.) It is entirely possible we may end up playing some games that are unbalanced in the other direction, since I think all valid ideas should be tested.
I would welcome any cogent arguments against my ideas, in the interest of making this game the best it can be for all concerned.