'Manufacturing' a gain to make use of CGT allowance

tl;dr Can I split a tracker, realise gains, and carry (un-realised) losses? What are the risks associated with it?

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Apologies in advance that this is quite lengthy and potentially not relevant to most. Feel free to point me towards a more relevant place to post if that seems wise.

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Last year I was fortunate enough to be able to make use of (most of) my annual CGT allowance.

This year, my investments (broad trackers) haven't produced as much return to be able to use the full amount, despite a larger amount invested.

I anticipate in the longer term that I will produce more capital gains over my life than CGT allowances I will have access to.

As such, I was wondering if the following was a sensible strategy:

1. Split a (single-fund) broad tracker (which I'll call $TRACKER) that I hold into a small number of funds that approach the same underlying holdings (which I'll call $PART1 $PART2 ...) but have different exposures.

2. Hold till the next tax year end.

3. Evaluate the $PART* holdings performance:

   1. All $PART* are down: That's rough, but no worse than if I'd held $TRACKER (no CGT allowance used)

   2. All $PART* are up: Sell any amount of $PART*s to crystallise some CGT gain. (some / all CGT allowance used). Same as if I'd held $TRACKER (or some composition of $TRACKER and option 3. below)

   3. Some $PART* are up, some $PART* are down - the interesting one. Sell the up sub-set of $PART* to crystallize a gain, and buy distinct funds that compose the same exposure as the up sub-set. This crystallises some gains, and carries some loss. The carried loss is then (in the long term) eventually paid by gains, but the crystallised gains benefits from the CGT allowance.

What risks might this strategy be exposed to?

The biggest one I can see is the ability to find sufficient $PART* such that I can decompose $TRACKER in multiple ways (and that the overall portfolio is actually aligned with the exposures I sought in $TRACKER).