Maybe it's just me who thinks this but isn't league's custom lobby making a bit too underdeveloped compared to other games? I mean, isn't the point of making a custom game to make a normal matchmaking game with custom rules, similar to a sandbox mode? At the current moment, apart from the practice tool (Singleplayer only), league only offers for multiplayer it's three maps (Summoner's Rift, Twisted Treeline and Howling Abyss) with the ability to change team size, type of champion selection (Blind pick, draft pick etc.) and who is allowed to spectate the game or not. There's not much room at all to have the ability to 'customize' the game, so to speak.
**What Other Games Have To Offer**
Other games, for example, Overwatch, gives it's players the ability to change and manipulate the rules of game modes, individual character's abilities and stats, as well as characters who are able to be played or not in their custom lobby/Gamemode. Something which League doesn't have, even though it is a free to play game when compared to Overwatch which you must buy to play. Money aside, even Dota 2 (a free to play MOBA) offers it players to create custom game modes (similar to Overwatch) but also the ability to create modded gamemodes that anyone has access to, E.g. Infinite ranged abilties, characters casting random abilities from other characters and much more (In all honesty I don't think League needs to go anywhere near as far as this but its just to put out an idea of what the competition is).
**If Updated, What Could This Mean for League?**
I believe that League's weakness at the moment, similar to all other MOBA's, is that matchmade games take alot of time and have the potential to go for far too long but also that there's not alot of freedom for player's who want to take a break from playing seriously in Summoner's Rift or Ranked all day. Although Nexus Blitz is now being added into the game which could potentially fix this weakness/issue, there are also those players who just don't find Nexus Blitz enjoyable or interesting. An update to the custom game creation options would allow all players to have the ability to create a custom game that they themselves will find equally or even more stimulating than what League has to offer currently. After an update to the custom game lobby is live, it could give inspiration or tell gamemode developers currently what it's players are interested in to help with the creation/adjustment of currently designed and future gamemodes. Bringing back older patches or older/removed gamemodes may help increase the playerbase by bringing back long time players.
**Suggestions for the Custom Lobby Update**
1._ The ability to change stats_
I'm sure all URF lover's would like this one. But the ability to change stats for specific characters or for a specific team on a % scale would be nice, could be used to make a 1 v 5 defeat the boss type gamemode.
2. _The ability to change team sizes or changing the number of teams_
This would be good for those who play League in a group with 10+ people. If the Hexakill gamemode is a possibility, why not a 10 v 10?
Changing the number of teams would be good too. It would allow people to create FFA gamemodes with many teams of single players or even many teams of small groups of players.
3. _Bringing back older maps_
Not sure how many people would enjoy this one but I'm more than sure that long time players of league wouldn't mind going back a few seasons and playing on the old map. Could also be could for those who want to make a gamemode based off of the maps of exclusive gamemodes or seasonal events like Nexus Siege, the removed Dominon map, Ascension, which I'm sure the Hide & Seek lovers of the game would enjoy or the christmas/Harrowing Rift maps.
4. _Preset Gamemodes_
Maybe adding all (or some) of the gamemodes that have been released to date as a preset option, at least those that wont be coming back in the future.
5. _The ability to change starting gold and experience, disable gold/experience gain and changing death time duration_
Could help with adjusting the length of the game. Especially helpful for those who want to play a quick/faster paced game.
6. _Disabling minion/specific jungle monster spawn, disabling turret fire/removing turrets, enabling turret invincibilty_
Helpful for creating gamemodes similar to the Hunt of The Blood Moon gamemode
7. _Changing the patch type of the game or reverting characters to older patches_
Could be helpful for those who dislike specific patches or want to relive the day before a rework or nerf.
Those are all the ideas I can think of at the moment. I'm sure others will comment their thoughts and ideas as well.
These are just my observations after playing the game for several years. It would be nice to finally have a more adjustable custom game to play with online players or with friends