The problem with boots of mobility

The boots of mobility became more affordable for supports since its nerf and price change. But there are some problems with them.

1. When you want to chase, you are clearly faster than your opponent (that's the point) but a single hit makes you suddently slower. If the enemy you chase has enough range to hit a ONE TIME, you lose your bonus, but also become slower than your enemy! This is like giving the enemy team a free CC!
2. And this is worse when you want to escape, when the action fails and you are already in combat and you want to get safe. If you do not have no innate mobility or long range CC (Leona, Soraka, Annie in particular), you are almost certainly doomed to die.
3. Another problem is that the loss of the movement speed also drastically decreases the effectiveness of % movement speed bonus abilities! For example, Karma's Inspire gives 60% movement speed. If you lose the 80 movement speed, the ability will give you 48 less movement speed. There is a difference of 128 movement speed that can be due to one minion hit!

Here are two ideas that could fix some problems:

• The minions don't cause the loss of movement speed. I can't count how many times I failed to chase/escape because ONE MINION on my path decided to hit me.
• Change the flat mobility bonus with a multiplicative % bonus. This could offer a better interaction with other movement speed bonuses, an opportunity to adjust the early threat caused by ultra-mobile roamer supports and a better uniformisation with the usual % movement speed bonuses given by objects (except boots themselves).

In both cases, the price shouldn't change [too much], to keep its affordable aspect.