Always a good question to ask.
Obviously, morality/ethics are personal/situational and a grey area. It's interesting to try to work out if something is moral/ethical with some critical questions. A good test of some behaviour, that is not explicitly precluded by the rules/laws that pertain is:
"What would happen if everyone did this?"
If the answer was "everything would be OK" then it's probably a reasonable thing to do. If the answer would be "complete chaos would ensue" then it's probably not good.
For example, you can go down the absurdist route and say "training is performance enhancing, so that is no fair". But if everyone trained, then the sport would still work.
But "If everyone dumps their bikes at the start of transition", then complete chaos would ensue. So it probably isn't a good thing
Obviously, there are some questions that this might fall down on, for example, if everyone puts £40k into the personal pension plans, thus avoiding 25% tax on that income, would we no longer be able to fund the NHS, education, social security safety nets etc. etc. Possibly, as the benefit is based on not everyone actually doing this - it's a "nudge" towards getting people to take this activity, which ends up benefiting wealthier people who can avoid to do this.
However, it's the sort of question that helps.
Other areas, are to what extent does this give me a personal advantage, while disadvantaging others. i.e. is this a "zero sum game", or not.
Again, aggressive tax planning doesn't (directly) disadvantage others. If Jimba pays £40k into his tax plan, it doesn't make anyone else poorer (directly, you can construct an argument about lower tax revenues leading to cuts in services, but that's a bit hard to ascribe to one person". If Jon.e drops his bike at the start of transition, again (if he is the only one doing it), it doesn't really deprive anyone else of anything (again, a complex argument could be constructed that he's taking 4 seconds off his time which could deprive a close competitor of a position, but that is a bit of a stretch to do that). However, if I arrive at the buffet for six first, and take all the scotch eggs, then I have deprived other people of stuff (zero sum).
Different questions, different answers, but always worth asking critical questions.