Interesting thoughts James.
Let me respond to some of them.
Massless black holes:
These were actually theorised by a number of physicists, these are believed to be what happens when a neutron star collapses, where the neutrons cease to exist afterwards therefore having a massless blackhole.
Oscilating Universe.
I have my own theory for this, once mass (as we know it) goes past a certain point, dark matter would begin to fill the hole left betweent he expanding mass and the center of the universe, once enough has done so the affect of gravity and dark matter pulling on the mass should brint he universe in, this is of course assuming dark matter is the force pulling against gravity like they say
Our Universe:
A lot of light which leaves from one place travelling to another is still effected by regullar invterval red shifting (natural red shifting) however, I will admit, light affected by gravity will also be subject to artificial red shifting, which would remove the ability to detect the age of the light and it's distance travelled.
Alternative form of propulsion:
Gravity fields are a VERY worth while effort in the form of propulsions..
I mean the more I think about it (I have a lot already) the more I realise it is necissary. There would not even be a feeling of movement inside a gravity field propelled vehicle, UFO's in general are great flying objects when you get down to the science of them.
The flying saucer just in shape is a great one, imagine if you will throwing a frisbie through the air, the spinning of the disk creates a gyro effect, which means any force attempting to divert the frisbie off it's course has to also deal with the momentum of the spinning body, a force ON TOP of it's directional movement.
After that, flying saucers, ufo's, hell I'll even say it outright, Government(s) or extraterestrial sourced flying means also have another advantage, which is the effect of gravity, any gravity fiels being projected in any direction will have a free fall feeling for a pilot, in other words.. no feeling at all. This allows for manouvers almost unimaginable to us right now.
It would be similar to the feeling a skydiver would feel, weightless as they travel towards the earth, without the wind resistance of course, kind of like how astronaughts practice in a large cargo plane going up and down equal in speed to the fall rate of gravity.
For each force of G applied no matter how fast either the person or the craft falls into that field, the effect of freefall will be the same, so the pilot will never really feel his own manouvers... making what we have seen UFO's do on T.V seem all the more realistic... as for your means of achieving it.. erm. I'm going to actually not comment on it.