I am afraid you are already too late.
The inclusionof lower teams was one of 5 items confirmed at the RFU AGM in April and WILL start in 2022-23.
See part of the circular sent out to Clubs in April from the RFU below. Full document is attached.
Adult Male Future Competitions Structure from season 2022/23
RFU Council voted on 27 November 2020 and 16 April 2021 to pass the following resolutions for a new competition structure in the adult male game from Level 3 and below.
The recommendations were proposed by the Future Competitions Structure Working Group following an 18-month review into the current competition structure, which has included extensive consultation sessions with Council Members, Constituent Bodies, Club administrators, competition organisers, match officials, coaches and players, in addition to webinars, a national survey and detailed analysis of available data.
5. Lower XV teams
From season 2022/23, Lower XV teams will be able to play in the English Clubs Championship up to and including Level 7, (no longer capped at Level

, subject to specific criteria to be set out in the RFU Regulations.
The addition of Lower XVs teams aims to offer appropriate competition opportunities for appropriate Lower XV teams, and to increase the number of teams in leagues at certain levels, which should decrease travel time for clubs and players.
For example, by grouping on a regional basis, a 2nd or 3rd XV team in Level 7 could be of similar standard to a 1st or 2nd Xv team in League 8 and they will now be able to compete against each other if they wish. This is voluntary. Clubs can sign up and will only be admitted if they fulfil the criteria, the detail of which will be confirmed in the implementation phase, but which is likely to offer some sensitivity to local needs.