You could potentially achieve your plans by making trade with lower developed empires more rewarding instead of blocking tech with everyone else. However with this way you might over do this slightly, but it still is a solution.
If leader board position 1 sends tech to second, first gets 1.1% more research points from experimenting tech.
If first sends to third, first gets 1.2% more research points from experimenting.
if first send the fourth, first gets 1.3% more research points from experimenting.
and you continue to scale the rewards with lower developed empires.
However, all this does is send tech to worse empires, first position will still develop there tech even faster than before now. But… this new physics of the game is just a setup for something else…
Because you can allow second the same rewards as first and last the same rewards as first. For example;
If second trades with third, second receives 1.2% more research from experimenting just like first does, so if seventh trades with eighth, seventh gets 1.9% more research from experimenting.
This physics makes sure it is rewarding to trade with lower developed empires as if you are in first place and you do not trade with bottom, but second places trades with bottom second will be at an development advantage. So second will be eventually able to easier challenge first on the leader board in terms of power. But all this still allows lower developed empires to “fairly” keep up with the top of the leader board.
But it does not have to be exactly like this, I am sure it is a good idea but there probably is better variations of the same thing.
This way would also even out unfair positions were the galaxy map was favouring certain positions… because if you start in an unfavourable position and end up not first on the leader board because of it, you still get a boost of some sorts.
However, technology does not put you first on the leader board because number of stars puts you first on the leader board. So it could create a new unbalance that I probably have not thought of.
EDIT: I suppose the problem with this is does the percentage stack every time you send a tech, because if first is logged in and no one else is, he is going to send his tech to everyone and get an 1 billion percent tech boost.
So no forget my idea. You could reward credits but the problem still is whoever is logged in is going to send all the tech first and no one else will be able to trade as much because everyone already has the tech.
But if you would like more ideas let me know.
EDIT: New idea to make the above work… if you send a level 2 tech to someone who already has a level 2 tech they receive research points based on how much the level 2 tech is worth.
So, if player eight has level 2 weapons and player seven sends player eight level 2 weapons, player eight receives the research points that level 2 weapons costed which goes towards level 3 weapons. And also player seven will receive 1.9% more points from experimenting.
Lets say you can infinitely send tech and the percentages will stack, so you need a new game mechanic for this to still be good… So, diminishing returns… The more tech you send per cycle the more expensive it is to send tech.