Does the defender lose all 300 clones in battle automatically? What if he loses a certain number, but there are some remaining?

This is a terrible idea!!

This system so far gives a massive advantage to the attacker and also encourages them to attack with the minimum number of clones because then they know their enemy won't get anything! This will also get worse in long distance combats and ill give you an example why:

As a winner I'm always going to lose 150 clones, be it from transport, deaths, or minimum kills. If I send more all I can possibly achieve by sending more is to potentially loose more clones and help my enemy reinforce their district against my next attack.

If I win I get to keep my clones, take some of theirs and only lose those dead in battle or transport. So why not aim over close zones and hit those further away instead of close by as I probably won't lose based on clone count and even if I do, I don't want to leave anything behind for my enemy.

My piece of advice would be is:

Start in these examples by telling us the game effect you are trying to achieve and I'm sure players will help you tweak your ideas in ways that will help you achieve them instead of just tearing apart your hard work.

Check how many clones the average skirmish map has right now, 150. Then count the number of times you remember losing a skirmish due to clone count. My bet its lot less often and very rarely is it when your winning the battle.

The only time I've ever seen a skirmish won by clone count when losing on MCC was when they had redlined the other corp but got redline sniped to zero because moronic blue dots kept zerging the redline and sniped.

You're right, I forgot to include the additional 25 stolen, I'll go back to change it, but it isn't going to affect the overriding point.

These incentives should come in the form of planetary bonuses or unique district bonuses (maybe for number held or number held in a system or on a planet) and not at the cost of further placing defenders at a disadvantage.

So all clones the attacker sends die regardless of how many you lose in the battle and how many you send? That makes it seem like "minimum clone loss" only ever applies to defenders (and calculations for clones stolen), since it's impossible to send less than 150 as an attacker anyway. I was under the impression the remaining get sent back to the attacking district.

This line from the wiki makes me think you're wrong "The losing side of a battle will lose a minimum of 100 clones. If they lose 125 during the fight that is what they lose. If they lose 75 during the fight then they will lose a total of 100 at the end." If attackers had all clones destroyed (whether or not they die in battle) when they lose but could only send a minimum of 100 anyway, then it should just read "The defending side loses a minimum of 100 clones if they lose" since it's already understood that the attackers lose everything.

The minimum clone loss could be 1 and the attacker would still lose all the clones he brought though (according to the way you're reading it), so it doesn't make any sense to apply "minimum clone loss" to the attacker numbers (other than for stealing clones) when all clones they bring die anyway after a loss.

I like the fact that CCP wants ppl to attack that is all well an good but one of my main concerns for PC is what happens when u say u reach the "limit" of ur ability to HOLD districts?

It would be nice if there was some sort of raiding mechanic that way u still attack and get paid for it but u wont be tied down with having to own another district u might not honestly want

Not everyone is interested or can hold vast amounts of space, some just want a small piece they can manage and just go raiding or doin merc work

The regular ISK payout will be based on the number of clones killed.

This is incorrect. The only ISK you get is from the clones being biomassed.