Haven't played an SG for quite some time, so I might be tempted... But spaceship takes a lot of time, especially a "self-reliant" one on DG... (Don't underestimate the tech prices on DG -- it's a quite significant difference to emperor.)
The only restriction is to disallow gifting backward civs to the next age for the sole purpose of us scalping their free, now reduced price, techs. 'Regular' tech trading is allowed.
I think this rule is going to cause trouble, because it's too "imprecise". How do you define "regular"...?
"You want to buy Magnetism for your world map? Fine! And how about Theory of Gravity for 2 gold? Excellent!" -- I think you get the picture...

Most often a deal like that would have the sole purpose of circumventing your rule... But not always: I have done such deals as real deals (even with non-scientific civs where there would clearly be no return on investment) in cases where I urgently needed 13 more gold to
- upgrade an urgently needed unit or cash-rush something urgently needed
- prevent my bank account from going below zero, so that I was able to run science at 10% higher and still finish a tech this turn instead of next
- see the map to find resources well in advance and be able to make plans on how to acquire them
- etc.
Also, in order to get a somewhat decent science rate going, you will need to trade for luxuries. Otherwise your science rate will stay at 30% for a long time... On DG you cannot simply roll over 2-3 neighbors quickly to get the required luxes, so you will have to trade for them. And the only way to buy these expensive things is to pay with techs! Have you thought about this important point already?
I can imagine that this rule is going to cause a lot of controversy. You'll need a lawyer in your roster, if you want to play under this rule...

If you want to try the real thing ("No tech trading. Full-stop."), I might be tempted to join. Alternatively you could go for a regular game (no trade restrictions) and up the ante to Deity?!