The issue you're talking about occurred to me as I was FIREing at age 46 in 2016 with perhaps 6-7 years in my Roth ladder. My Roth ladder was all in VTSAX.
What I chose to do, which wasn't really very strategic or smart, was to leave it in VTSAX and offhandedly figure that either (a) SORR would not hit me during the applicable time frame, or (b) I could earn some side gig income, or (c) I could just pay the 10% penalty and access my traditional IRA early.
What happened over the past 4-5 years is that (a) SORR did not hit me; in fact, VTSAX has done very well since I retired, (b) I earned some side gig income that has cut my WR in half and extended my Roth ladder quite a bit, (c) I had time and energy and lower stress levels so I could optimize and reduce my spending even more, which also extended my Roth ladder quite a bit, and (d) my Mom passed away and I received some life insurance, which deferred my Roth ladder for a while.
You could say I got lucky financially, and I wouldn't argue with you. But it has also occurred to me over the years since I retired that my FIRE plan assumed the worst outcome for pretty much everything, so it wasn't really surprising that the absolute worst didn't happen. On average, results are average, not worst case.
Based on the way you're writing about it, it sounds like you want to keep the money at Fidelity and relatively safe. If I were in your shoes, I'd figure out what the Fidelity equivalent of VBTLX is and put it in there. Some might argue that bond funds may not do well in a rising interest rate environment; I would argue that nobody knows if we are or will be in a rising interest rate environment over the next 5-8 years. About two years ago the Fed was on a march to raise their target rates to 4%. If you did something like that then you'd just consider that part of your 40 bond allocation.
One minor note: from the IRS' point of view, you have one logical Roth IRA, even if you have multiple Roth IRA accounts. Any withdrawals from any Roth account will be your contributions (oldest first), then conversions (oldest first), then earnings. From a tax point of view, the IRS doesn't care in the slightest which Roth you withdraw from, nor what you sell inside the Roth when doing so. So for example, if you withdrew funds today from your new Fidelity Roth IRA, the IRS would consider that withdrawal to be from your first contribution to your oldest Roth IRA. You don't have to think about it that way if you don't want to, but that's how the IRS looks at it and how your taxes will turn out.