I always thought it was odd that we don't have a pokemon trainer type summoner in the game. Would be a fun addition. Especially if putting points into either R or Q/W/E caused the summons to evolve into different models with increasingly powerful abilities.
My idea was that Q/W/E has 6 levels, R has none. R's effects level with either Q/W/E or character level.
Q/W/E each summon a different companion (probably elemental style, or maybe even elemental armor, but that seems too close to Udyr) and had different effects. Q would only use Q's main ability, W would use only W's main ability, E would use only E's main ability. R would be unique to which companion was summoned but have a global cd for all 3 summons. A delay between summoning and using abilities would allow them to be quite powerful without feeling like the spammy annoyance of Yorick.
All numbers are made up BS and not properly balanced. Just there to give an idea.
Passive:
Summoning a new elemental disables all other elementals for X seconds (disable time decreases based on character level).
Using an elemental's ultimate ability (R) exhausts them, sending that elemental back to its realm after (5-10 seconds?) and disabling it for X seconds (same amount of time as R's cooldown). During this time, your connection with the other elementals grows stronger, increasing their ability's effects by X% (based on character level).
All summons have a basic attack with no special effects. Q - Melee Attack, W - Melee Attack, E - Ranged Attack. The summoner may not use his/her basic attacks while an elemental is summoned. Movement of the elementals would be unique in that it REQUIRES you to have a "command pet" shortcut enabled (clicking R like one would with Tibbers to reposition would not work since all summons have active abilities) increasing the skill floor and skill cap (having to position two characters is way harder than just one). The "Summon X" abilities are auras that never go away as long as the elemental is alive.
Summon Q: Fire Elemental. Moves at the same speed as the summoner. Obvious damage pet. Does AoE damage that applies a stacking DoT up to x stacks (maybe x = skill level?)
**Activated Q: **Spits fire in a line, leaving a DoT AoE (stacks with passive) where the fire touched the ground (fun interaction: doesn't leave behind a trail in water). Upgrading the skill level adds another line in a frontal cone area. Level 6 skill turns the ability into a ~120 degree cone AoE instead of lines (similar to Shyvana's E).
**R: **Summons a meteor style attack at targeted location after a slight delay (think Veigar W so that you can't just nuke someone out of the blue). Leaves behind a large burning scar on the rift, about 50-100% larger than the meteor, dealing AoE DoT (stacks with passive and active, totalling 3 DoTs possible).
Stats: 1.2x total AD and AP, 0.8x armor and MR, 0.8x HP, move speed equal to character.
Summon W: Ice Elemental. Moves more slowly than the summoner. Obvious tank pet. Gives off a stacking AoE slow (no damage) every 0.5s. After receiving 5 stacks, you can use the activated W.
Activated W: Opponents are frozen solid (like Sejuani ult) then become immune for some time to both the slow and freeze (time immune scales with W level)
R: Some sort of blizzard. Anivia's R style AoE but much larger (maybe size scales with level), centered on the elemental, no (or very small) slow effect, low damage, and reduces sight range based on level (maybe by 5% per skill level). Lasts for a few seconds. Should also apply the passive stacks.
Stats: 0.8x total AD and AP, 1.2x armor and MR, 1.2x HP, -20% move speed.
Summon E: Lightning Elemental. Moves slightly faster than the summoner. Support pet. Nearby allies gain stacks of some static-y thing, giving increased movement speed. Caps out at some number of stacks, (only at max rank) giving a bigger boost in speed for a second or two then debuffs with immunity to the boost, duration of which is based on skill level.
**Activated E: **Instantly grants all allies in range max stacks of the passive and grants them immunity to the debuff associated with it for a few seconds. Skill level determines max number of stacks and duration.
R: Revitalizing Jolt. Think more so of saving lives here than taking them. In a small AoE around it, would remove all CC for allies, grant them immunity for a very small duration (like 0.25s small) and heal them (or not if it wasn't easy to balance, should be a very small amount, like 1-2% per stack + 0.5-1% AP per stack) based on how many stacks from E's passive they have (won't work if they're debuffed from the passive, making it more strategic).
Stats: 1x AD and AP, 1x armor and MR, 1x HP, +20% move speed.
Just having a champion like this would add a pretty neat counter to some champions who are unbearable to play against (Yorick, Yasuo and a few others) by giving you literal bodies to throw at them. The champ itself would have to have very low base stats (starting off with between 300-400 hp, maxing out at 1500-1600 tops before items).
Anyways, just me rambling on about something I came up with when bored.
tl;dr: Posted a champ concept I came up with for a league-specific summoner style champion.