Time is a manmade construct, while gravity is a natural phenomenon, it would be wrong to confuse the two or to equate them on the same terms. Repeated experiments have confirmed the effect of gravity on clocks and the results seem to agree with this reasoning, namely that in a stronger gravitational field things, including atoms, are more restricted than in a weaker gravitational field. As expected, time would move faster on a space ship far from any gravitational fields than it would on earth. Therefore, it would appear that time as measured by clocks is solely dependent on gravity or (with reference to the equivalence principle) on the rate of acceleration of the vehicle in which the clock is situated. This being so, (time being a manmade construct) and since the exact deviations due to the influence of gravity (or acceleration are known. It is possible to adjust clocks in order to compensate for the distortion due to gravity or rate of acceleration, this would result in a Universal time. Time for everyone would be the same, since everyone would have the same frame of reference. Since everyone occupies the same frame of reference, time dilation and length contraction are not present. While physical effects due to traveling under great acceleration might result in funny effects akin to the twin paradox, surely this could be written down as an effect of travelling at high rates of acceleration rather than to time dilation?
This raises the question of whether humans will be able to survive under the G- forces necessary for such changes in time to take place. A pilot can experience up to 9 G’s in a modern jet fighter, this equates to 317 km/h/s (kilometres per hour per second). So it’s increasing its speed by almost 317 kmph every second! While a speed of 320 Kmph might be very fast on earth, it is not very fast when it comes to space. For instance the space station has an orbital speed of about 25,000 kmph! Yet, the astronauts inside the space station experience near zero G forces but that is because the space station is in free fall and the effect is the same on astronauts as may be experienced by objects in a free falling lift. What is clear is that under forces of very rapid acceleration, as would be needed to reach near light speeds, survival would be problematical.
As for gravity changing with pure velocity where the effects of acceleration are not present, this is very much a moot point. For instance in the space station, theoretically an acceleration is taking place since the orbit of the space station requires constant directional changes, yet this is not reflected, either in the clocks or in the astronauts. Because the space station is still under the influence of the earth's gravity. Similarly, on the Apollo missions, even though the space ship was considerable distances from earth, the astronauts still experienced weightlessness for the same reason.