Here is the rule addition that I recommend (this was talked about in the HINQ discord, so I am basically paraphrasing from there and am also adding more stuff, and complicating it a bit more by giving the disconnected side the choice) (of course the wording can be reworked, I just attempt to explain the concept):
1. In case there is a crash during a round, the team that had the crash can request a restart. This rule comes into effect only if the crashed side requests it.
2. When the crash occurs (before or during the fights started) the restart may be prompted. The team that had the disconnected player may decide to keep fighting for that round and then ask for a restart after the round in which the disconnect happened (so disconnected team does not lose the chance to ask for a restart and if they had the advantage on the disconnect round, they can keep fighting)
2a. If the disconnect happened during a team fight, to prevent any confusions or disagreements, the team that had a disconnect will have to cease fighting (if the disconnect occurred during a team fight and they want a restart) (not all members of a team will know each rule in detail so, its not a crime if they do not stop fighting, but the IGL must stop fighting and write in chat they want a restart). Lets say the disconnected team is winning 2-0 and has the economy advantage, they can, if they choose, try to win with 5v6, but if they want a restart, the score immediately goes to 2-1 and the opposing side gets all the econ possible (so 300 gold vs 380 gold).
2b. If the team that was winning 2-0 (the score is just an example not part of the rule) decided to try to win with 5v6 but ended up losing the round to make it 2-1, they can request a restart for the following round, but the score goes up to 2-2 and the other side gets the max eco advantage (so 300 vs 380 gold).
2c. If the team that had a disconnected player decided to keep fighting when the disconnection occurred and they ended up winning the round, a restart may be made without needing rule 5. Just go ahead a restart the game with no need to watch for economy.2d. If the disconnection happens at the very start of the set (before anyone has any score or kills) the disconnected side may request a restart without any penalty (I feel like this is a bit open to exploitation since, if the opponent side sees a disconnection, they can decide to pounce on the disconnected side to get some score and kills in order to try to demand them to give 1 point and start with economy, so IGLs need to immediately request a restart and start leaving the game, before an enemy couch kills one of their guys).
3. If both sides had a crash, then it is not necessary for both sides to agree to a restart. If one side wants a restart, a restart is given (with eco adjustments) as long as it is in line with the aforementioned rules.
4. On the restarted round (lets call this round murder round), disconnected side will drop all their weapons (this is not a rule, do it however you want, just make sure opponent side has no deaths and the disconnected side has no respawns left) and let the opponent team kill them (as many times as it takes) to ensure max eco for the opponent side and minimum eco for the disconnected side.
5. On the murder round the disconnected side will spawn as the cheapest units and spawn as many times as they can. At the end of the murder round each player in the opponent team must have same number of kills, and score. So there is no room for exploitation. (this rule is put due to an exploitation that may occur: Some people are competing at the stats table and the team that did not have a disconnect can easily pump up the numbers of one of their players by making them kill all the disconnected side. So we either do not count the murder round as part of stats (which could be complicated I imagine, if I am wrong rule 5 is not needed I guess) or use this rule.
I think these cover all angles and prevent exploitation of the rule. Let me know if I missed something, we can add it, discuss it etc.