Is there an efficient way to filter an iCal feed to overcome 1 MB limitation to subscribe into Google Calendar?

Question

I have a script running in Google Apps Script that, among other things, reads events from several Google Calendar calendars subscribed on my account. There is another calendar I need to read events from but it's from a colleague's iCloud calendar that he has shared with me by giving the public iCal/Webcal link. However, I cannot subscribe to it in Google Calendar because the ICS that can be downloaded through this link is approximately 3 MB and Google places a 1 MB limitation.

Is there a strategy through some middle-man service or software that I can implement, self-host, or pay that will allow me to do the following?

1. Subscribe to the iCloud calendar's webcal link
2. Filter the events by date period to a more limited range
3. Provide a new webcal link that produces an ICS that's less than 1 MB