Sanguine Blade is NOT a splitpush item [with idea for fix]

The current version of Sanguine Blade out on the PBE is an item for getting picks on bushes, not for splitpushing. I will explain why.

You only get its passive if you attack an isolated target. Basically, in a splitpush scenario, this means that in order to unlock its passive, means you have to fully clear the minion wave before fighting. From my experience playing Tryndamere [my main], Poppy, and Garen (all pretty good at splitpushing), if you clear the minion wave to push into turret and you are ahead of your splitpush opponent, they are not going to walk up to you regardless (unless they have teammates so you wouldn't keep the passive anyway), so fighting them right after you clear the minion wave isn't an option.

Another HUGE part of splitpushing: Diving your splitpush opponent when you are ahead of them. If your team engages in a 4v4 on the other side of the map and you need to make an impact, then you want to dive the enemy splitpusher so you can take objectives while your team fights, regardless if they win or lose. Well, this passive pretty much says "no diving allowed". Turrets are counted as part of isolation, meaning you will not get the attack speed passive during a dive.

sidenote Also, clearing waves with tiamat doesn't give the passive so it makes your waveclear less efficient if you want to auto last minion): end sidenote

Solution I propose to make Sanguine Blade less catered towards finding picks in bushes with dark harvest Kha`Zix or full crit Yi, and more directed towards being more powerful when away from your team (what splitpushing actually is):

Sanguine Blade passive activates [2 - 1 seconds, based on champion level] after damaging an enemy champion or structure (like old Conqueror) and lasts for five seconds; duration is refreshed on every basic attack. Effect is immediately disabled if any of your teammates enter a 1500 unit radius. Mousing over the item shows the range of this on the minimap like other large-radius abilities.

You might be thinking, "That sounds broken, you always have it up". Not really. The way I suggested it has a very large degree of strategic counterplay associated with it, if you read into it. By checking the effects currently active on the enemy splitpusher with this item, you can see if they have teammates nearby shadowing their splitpush, depending if they have the Sanguine Blade passive up in their buffs. This gives info as to where the enemy team is, and lets you, the splitpusher, know whether this is an unquestioned 1v1 battle with no chance of sudden interference. Besides, in this current version, you never have it up except if someone facechecks you or walks up after you clear a wave or jungle camp - basically, it's a braindead low elo stomp item that you can still make use of with your entire team sitting right next to you in the river bush waiting for the enemy support to ward baron (nice splitpush btw).

tl;dr: Passive always active if no teammates nearby (splitpush) instead of on isolated enemies (picks).

Leave thoughts down in the comments, would like to see other people's ideas on how to make this an actual splitpush item.